AT 213
Chapter 1: Safety
Clean Air Act & Certification
• Began in 1990
• Restricts Ozone depleting elements in A/C refrigerants
• By 1992, R12 was only sold to certified technicians
• R12 was stopped being manufactured at the end of 1995
• EPA works closely with the CAA to enforce laws and set up certification standards
o ASE
o Mobile Air Conditioning Society (MACS)
Refrigerant Safety
• High pressures in storage containers and A/C systems can cause severe injuries
• Temperature effects pressure
• Explosion can occur if pressures are exceeded
• Fluid pressure or Hydrostatic Pressure can penetrate the skin
• Refrigerant in the eye can cause freeze the eye and cause blindness
o Don’t rub eyes
o Flush with cool water
o Cover eye and seek medical attention
• Refrigerant on the skin can cause frostbite
• Excessive refrigerant in the atmosphere in confined spaces can cause drowsiness or unconsciousness because it reduces the oxygen
• Refrigerant that comes in contact with an open flame or hot surface creates a toxic gas called Phosgene
o Safety Rules
 Never heat refrigerant above 125 degrees
 Keep refrigerant away from high heat or open flame
 Always wear eye protection (face shield recommended)
 It is illegal to release refrigerant into the atmosphere (R12)
 Never mix refrigerants
 Use only DOT approved containers and properly label them
• Approved tanks have burst valves to prevent explosion
 Work in a well ventilated area
Antifreeze/Coolant
• Four primary characteristics of antifreeze/coolant
1. Freeze protection
2. Boil protection
3. Corrosion prevention
4. Heat transfer
• Two main types of antifreeze/coolant
o Ethylene Glycol-based (EG)
o Propylene Glycol-based (PG)
 Standard (2-3 years; 30,000-45,000mi)
 Extended Life (5-15 years; 100,000-150,000 mi)
 Prevents corrosion build-up
 Prevents build-up of hard water deposits
 Raises boiling point
 Lowers freezing point
 Draws heat away from internal parts through a “heat-sink” effect
o Electrolysis
 Build-up of voltage in the cooling system (.3 volts or higher)
 Causes erosion of metal and gaskets
 System must be flushed and coolant replaced
 Never mix standard and extended life coolants
o Recommended Mix
 50/50 (-34 degrees freeze point)
 60/40 (-54 degrees freeze point)
Hazardous Material Safety
• Antifreeze/coolant must be disposed of properly
o Causes kidney damage if ingested
• Refrigerants must be properly labeled and stored in DOT approved containers
• Refrigerants marked with “CI” or “F” have Halogens in them and should be considered toxic. Keep away from open flame or hot surfaces and conditions
AT213
Heating & Cooling
Cooling System Operation
• Conduction
• Convection
Coolant Flow
• Standard Flow
• Reverse Flow
Radiators
• Construction
o Tanks
o Oil cooler
o Tubes and fins
o Cores (2 core, 3 core, 4 core, etc.)
• Design
o Down Flow
o Cross Flow
• Radiator Failure
o Leaks in the core from physical abuse
o Leaks in the core from corrosion or electrolysis
o Leaks between the core and tank
o Cracked or damaged tank
o Leaking transmission or engine oil cooler inside the tank
o Damaged fins
o Plugged fins from foreign material
o Plugged tubes/fins from corrosion build-up
• Radiator Cap & Overflow/Expansion Tank
• System Servicing
o Visually inspect for leaks, external damage of radiator and recovery tank
o Visually inspect for corrosion build-up in radiator core
o Pressure test & inspect cap
 Potential problems when a cap fails
 Inspect sealing surface of cap on the radiator neck for nicks or damage
o Inspect radiator shroud for damage and proper mounting
 Potential problems of a non-functional shroud
 Can increase cooling up to 30%
o Bleed air from system after adding coolant or servicing
 Many systems include air bleeds
 May have to loosen a hose at the highest point in the system
Water Pumps & Coolant Passages
o Coolant Passages
o Siamese cylinders
o Expansion Plugs
 Expansion plugs are not freeze plugs. These plugs are not designed to protect against a cracked casting in the event of freezing coolant
 Expansion plugs often rust through or leak from corrosion build-up and rust in the cooling system
 When servicing expansion plugs, high quality case sealer should be used on the plug and block surfaces before installing (do not use silicone)
o Reverse Flow Theory
• Water Pump
o May be driven by a drive belt or timing belt
o Circulates the coolant through the block and radiator
o Impeller
• System Servicing
o Check pump shaft for loose bearing if accessible
o Inspect drain hole for signs of leaking
o Inspect expansion plugs for signs of leaking
o Pressure test system to inspect for leaks
o When replacing pump:
 Inspect cooling system for contamination or foreign material that could cause new pump failure
 Compare new and old pump, including the impeller fin direction
 Inspect mounting area of pump for erosion or damage
 Take care when using sealer not to plug cooling passages
 Replace timing belt driven pumps when servicing the timing belt
 Do not over tighten belts causing premature bearing failure
Thermostats
• Operation
• Types
o Solid Expansion
o Bimetallic
o Bellows-type
• Service
o Quick and severe overheating may be caused by a stuck-closed thermostat
o An engine that never reaches normal operating temperature may be caused by a stuck-open thermostat
 Note temperature gauge
 Low heat output in passenger cabin
 Poor fuel economy
 Failed emissions
 Check-engine light due to delayed closed-loop
o Check opening temperature by measuring heat on both sides of the thermostat
Heating & Cooling (cont)
Fans & fan Assemblies
• Airflow can make up to a 30% difference in cooling system capacity
Fan Shrouds
• Directs all air movement through the radiator for more efficient cooling
Fans
• Ridged Fans
• Flexible Fans
• Clutch Fans
 Non-thermal
 Thermal
 Thermal clutch fans allow a wider RPM range for maximum efficiency and minimal horsepower loss
 Clutch fans allow for smaller water pump pulleys to be installed, increasing coolant flow, without losing horsepower to excessive fan speeds
• Electric Fans
• Fan Service
 Visually inspect fan blades for cracks, looseness or missing pieces
 Inspect water pump shaft or mounting for loose bearing
o Clutch fan should not move more than 1/8th of an inch
 Inspect clutch assembly for leaking silicon, lock up, or free-wheeling
 Install “timing tape” on the fan blades and read fan RPM
 Inspect fan shroud and air baffles for cracks, loose mountings or broken and missing pieces
 Check electric fans for seized or damaged motors
 Test thermostatic switches for proper operation
 Check operation of A/C bypass circuit
Belts & Hoses
• Belts
o V- Belts
 V belts are measured in pitch and width.
 Pitch
 Width
o Serpentine Belts
 One belt drives all the accessories
o Belt Service
 Cracks
 Glazing
 Oil contamination
 Stretch
 Pulley wear
 Pulley Alignment
 Belt Tension
 Tensioner operation
 Proper belt routing
 Checking for belt noise
• Hoses
• Servicing
o Look for kinks in hoses that could cause restrictions or hose failure
o Check for hard or brittle hoses due to excessive heat
o Check for soft or swelling hoses due to oil contamination
o Check for cracks in the hose due to stress or electrolysis
 Electrolysis cracks from the inside out
 Cracks are usually seen an inch or two from a metal mounting
 Green residue at the hose ends may be a sign of internal break-down
o Check for stretched hoses due to broken motor mounts or wrong application
o Cut hoses off when removing them to avoid damaging other components
o Don’t over tighten hose clamps
 Over tightened clamps can cut a hose
o Spring clamp pliers
o Hose clamps should always be placed next to the raised area of the connection for maximum holding power and reduced corrosion build-up
Heater Systems
• Heater Core
• Potential Problems
o Leaks are the most common problem w/ heater cores
 Wet carpet under the core in the interior
 Coolant on the ground under the evaporator drain
 Steam on the windshield during low speed blower operation
 Damaged inlet/outlet fittings due to improper hose service
o May become plugged from dirty coolant or contaminants
o Cold air due to low coolant level
o Engine overheating due to heater core restriction
• Heater Control Valve
 Manual shut-off valve
 Cable operated valve
 Vacuum operated valve
 Thermostatic control valve (electric solenoid)
Engine Overheating
• Low coolant
• Stuck closed thermostat
• Restricted radiator (internally)
• Restricted radiator fins (externally)
• Restricted water jackets in block or head
• Damaged water pump impeller
• Broken or missing fan shroud
• Plugged heater core
• Faulty clutch fan
• Faulty fan switch (electric fan)
• Seized electric fan motor
• Plugged exhaust
Cooling System Additives
• Stop-leak
o Good or bad?
o When to use?
Cooling System Flushing
• Without Flush Machine
o May use an additive to loosen up contaminants
o Drain radiator and block
o Fill with water and warm to operating temperature
o Drain radiator and block again
o Fill with water and run engine to operating temperature again
o Drain radiator and block
o Fill system with 50/50 mix of coolant and water
o Turn on heater and run engine to operating temperature
o Bleed any air from the system
o Verify that no leaks exist
o For a more extensive flush, remove the thermostat and reverse flush the block with water until exiting fluid is clean. Reinstall thermostat and fill system
• With Flush Machine
o Drain radiator
o Siphon coolant from recovery tank
o Connect flush machine between upper radiator hose and radiator
o Fill flush machine with water
o Cycle machine to fill the radiator with water
o Install the radiator cap and start the engine
o Recover the old coolant until clear water comes out
o Stop vehicle and fill flush machine with 50/50 coolant mix
o Cycle machine to fill system with new coolant
o Relieve system pressure, remove radiator cap and lower coolant level below upper radiator hose
o Disconnect the machine and reconnect upper radiator hose
o Top off radiator and recovery tank levels
o Run vehicle with the heater on and check for leaks or air in system
AT 213
A/C System Components
A/C System Operation
• Theory
o When air or liquid is compressed, it is heated by the energy of compression
o The temperature can then be lowered by cooling through a radiator
o When cooled, if the liquid or air is then brought back to atmospheric pressure, the temperature will significantly drop
o Automotive air conditioning works on this principle
A/C Components
• Compressor
o Circulates the refrigerant through the system
o Raises the pressure of the refrigerant from 20 psi to 220 psi
o reed valves
o service valves
 R12
 R134a
 Schrader valve
• Front seated
o Clockwise – all the way in; valve closed; gauge line closed
• Back seated
o Counterclockwise – all the way out; valve open ; gauge line closed
• Mid-position
o Compressor lines open; gauge line open
• Condenser
o Removes the heat from the compressed refrigerant
o Located in front of the radiator
• Serpentine flow –
• Parallel flow –
• Receiver-Drier
o A storage tank for liquid refrigerant
o Used on systems with an expansion valve between the high and low sides
• Accumulator
o Located on the suction side of the system (big line)
o Holds excess liquid refrigerant to allow only vapor to travel to the compressor
o desiccant bag
• Expansion Valve
o Separates the high and low side
o Used in systems with receiver-driers
o Block Valves –
• Orifice Tube
o Separates the high and low side
o Used in systems with an accumulator
• Evaporator
o Located inside the vehicle in the air ducting
o Receives low pressure liquid refrigerant through the expansion valve or orifice tube to cool the vehicle interior
o Flooding
o Starving
• Lines & Switches
o May be solid steel, aluminum or copper
o Some are high pressure rubber with crimped fittings
o Early style rubber lines for R12 may not be compatible for R134a
 R134a contains smaller particles in its composition which can penetrate older lines without a nylon barrier
o Hoses on vehicles made prior to 1992 should be replaced when retrofitting to R134a
• Suction Line
• Discharge Line
• Liquid Line/High Pressure Line
• Pressure Switches
o High side
o Low side
A/C Circuit & Operation
• Expansion Valve System
1) Compressor draws in low pressure vapor
2) High pressure vapor leaves the compressor and goes to the condenser
3) High pressure vapor changes to high pressure liquid as it cools
4) High pressure liquid travels to through the receiver-drier where moisture is removed and only high pressure vapor is allowed out
5) High pressure vapor travels to the expansion valve where it is metered out and lowers the pressure
6) Low pressure liquid travels from the expansion valve to the evaporator
7) The evaporator picks up heat from the air traveling across it and carries it back to the compressor
8) Cycle repeats
• Orifice Tube System
1) Compressor draws in low pressure vapor from the accumulator
2) High pressure vapor leaves the compressor and goes to the condenser
3) High pressure vapor changes to high pressure liquid as it cools
4) High pressure liquid travels through the orifice tube where it is metered out and pressure is lowered
5) Low pressure liquid travels from the orifice tube to the evaporator
6) The evaporator picks up heat from the air traveling across it and carries it to the accumulator
7) The accumulator traps liquid refrigerant and only allows vapor to exit to the compressor – also removes moisture from the system
8) Cycle repeats
AT 213
Chapter 6: System Service & Testing
Refrigerant Contamination
• Identifier
o Tests refrigerant for purity
o Must be at least 98% pure
• Sealant Contamination
o Seal sweller
o Stop leak
• Air Contamination
• Causes:
• Moisture Contamination
• Causes:
• Vacuum should be applied for 20-30 minutes and should hold when the pump is turned off for 5-10 minutes without bleeding off
• If excessive moisture is found in the system, the receiver-drier or accumulator should be replaced
Leak Detection
• Soapy water
• Visible Dye
• Black-light Dye
• Electronic Halogen Leak Detector
o A small hole drilled into the evaporator box allows access to detecting leaks in the evaporator core
Moisture & Removal
• Moisture
o Refrigerant reacts with water to form hydrochloric acid.
 The acid is very corrosive and damages all metal parts including copper, aluminum and steel
o Maximum allowable moisture content in the A/C system is 10 ppm
 One drop of water in a 2 lb system equals 60 ppm (6 times allowable)
 Preventing Moisture
• Moisture Removal
o Achieved by using a vacuum pump
o Pump is connected to both the high and low pressure lines of the system through the service valves
o Vacuum lowers the boiling point of water and causes it to boil
o The vacuum pump removes the moisture in the system in a vapor state
o 25-30 inches of vacuum should be maintained on the system for 20-30 minutes
o The pump should then be turned off and the system monitored for 5-10 minutes to see if vacuum drops off
 A loss of vacuum indicates a leak in the system
o If the system checks out ok, it is now ready for charging
Recovery & Recycling
• Recovery
o The removal of any refrigerant from the system to be stored and not reused
 Make sure all valves are turned off on the tank and gauges
 Connect hoses to the high and low sides
 Connect yellow hose to the machine inlet (if applicable)
 Open the valves for the tank and gauges
 Turn on the machine and push the recovery switch
 Machine will stop when the system is recovered
 Drain the oil into the container and measure for recharging
 Turn off the tank and gauge valves and disconnect
• Recycling
o The process of removing moisture and foreign material from the recovered refrigerant to be reused in the A/C system
 At least 8 lbs must be in the recovery tank
 Open both valves on the recovery tank and turn on the recycling switch
 Operate until the sight glass indicates that the refrigerant is clean
 Bleed any air out of the tank as necessary
 Turn off the recycling switch and both tank valves
A/C System Performance Checks
o Belt tension & Condition
o Clutch Operation
o Is the clutch cycling on?
o Does the clutch slip when engaged?
o Is there oil or dirt on the clutch?
o A slipping clutch could be caused by improper air gap, contamination to clutch surface, or voltage problems at the clutch coil
o Does the clutch rapidly engage and disengage? (low charge)
o Electric Fan
o Blower Motor
o Cabin Air-flow
o Sight Glass (if applicable)
o Is it clear?
o Are there bubbles when the system is operating? (air)
o Is there foam? (low charge)
o Is there streaks? (no liquid refrigerant; low charge)
o Low-side Line
o Is it cold?
o High-side Line
o Is it hot?
o Leaks
o Damaged tubes or hoses
o Damaged fittings or line switches
o Leaking Schrader valves
o Oil around fittings or O-rings indicating a leak
AT 213
Chapter 7: The Refrigeration System
System Charging
• Adding new or recycled refrigerant to the A/C system
• With Recharging Station
o Look up system requirements for refrigerant
o Insure all valves are closed and connect a manifold gauge set or the machine hoses to the high and low sides of the system
o Turn on the machine and input vacuum time
o Input amount of refrigerant to be used
o Open both manifold valves and both tank valves
o Start vacuum process and allow to pull for a minimum of 20 minutes
o When vacuum is complete, monitor for 5-10 minutes to insure that vacuum holds
o If vacuum holds, begin charging
o When charging is finished, close all hand valves
o Start vehicle, turn on the A/C and check pressures and cabin temperature
o If additional refrigerant is needed, use the “add” feature to add an additional 0.2 lbs of refrigerant at a time, checking the system after each addition
o If pressures and temperature are ok, disconnect hoses and turn off the machine
o Replace service valve caps
• Without Recharging Station
o Look up system requirements for refrigerant
o Insure all valves are closed and connect a manifold gauge set to the high and low sides of the system
o Connect the yellow service hose to a vacuum pump
o Pull vacuum on the system for a minimum of 20 minutes
o When vacuum is complete, close both hand valves and monitor for 5-10 minutes to insure that vacuum holds
o If vacuum holds, disconnect service hose and connect to refrigerant tank or individual cans
o Purge air out of the service line by cracking the fitting where the yellow hose connects to the manifold set
o If refrigerant is introduced in a vapor state, both high and low side valves may be opened
o If refrigerant is introduced in a liquid state, only the high side valve should be opened
o Add the system required amount of refrigerant to the system
o Close both hand valves on the manifold gauge set
o Start engine, turn on the A/C and monitor gauge pressures and cabin temperature
o Add additional refrigerant if needed
o When pressures and temperature are ok, turn off vehicle and disconnect hoses
o Replace service valve caps
o (Note: If refrigerant is to be added when the vehicle is running, only the low side is to be opened and the refrigerant tank or can should not be inverted. Inverting the can will allow liquid refrigerant into the compressor and may cause damage)
Defective Components
• Evaporator
o Plugged core; dirt or debris in the fins
o Cracked or broken evaporator case
o Leaking seal or o-ring
• Compressor
o Noise
o Seizure
o Leaking seals or gaskets
o Low suction from a low charge or restriction in the low-side line
o High suction and low output caused by defective valves or gaskets
• Condenser
o Leak from physical damage or corrosion
o Internal restriction from damaged tube
o External restriction from dirt or debris in the fins
• Orifice Tube
o Restriction from a clogged screen
o Restriction from a broken tube
• Expansion Valve
o Restriction from a clogged inlet screen
o Stuck open or closed valve
o Defective sensing bulb or bulb that is not making contact with the evaporator
System Diagnosis
1. Normal Operation
o Low-side 15-35 psi
o High-side 160-220 psi
o Cabin air temperature 35-45 degrees
o Compressor cycles normally
2. Low, low-side; normal to low high-side
o Inoperative or out-of-adjustment thermostat
• Evaporator icing caused by a stuck-on compressor clutch or an expansion valve sensing bulb that is not contacting the evaporator
o Low-side restriction
• Check along the low-side lines for temperature; should be cool to cold between the metering device and the compressor; warm spots indicate a restriction
o Plugged orifice tube or expansion valve screen
• Check along the high-side lines for temperature; should be warm from receiver-drier or condenser outlet to expansion valve or orifice tube; cold spots indicate a restriction
• Turn off A/C for 10 minutes and then turn back on; a restriction will show abnormal gauge readings immediately
o Excessive moisture in the system
• Metering device inlet is very cold due to freezing moisture
• Turn off A/C for 10 minutes and then back on; if moisture is the problem, gauge readings will be normal for a few minutes before reading abnormal again
• Receiver-drier or accumulator must be replaced
o Low refrigerant charge
• If both gauges read low, system may be low on refrigerant
3. Very low, low-side; low high-side
o Clogged inlet screen
• Compressor is tying to pull refrigerant, but can’t
• Low-side may even show vacuum
o Defective valve or tube
• A broken orifice tube can cause a restriction
• Expansion valve may not be opening properly
o Sensing bulb may be defective
o High-side restriction
• This condition will cause a high reading on the high-side gauge
o Excessive moisture in the system
• Causes corrosion and rust particles to form that may plug the system
4. Low, low-side; high, high-side
o High-side restriction
• The closer to the compressor, the higher the pressure
• Condenser, orifice tube, receiver-drier, etc.
• Check for temperature changes in the line
5. High, low-side; low, high-side
o Refrigerant not circulating
o Electrical
• A/C power switch
• Pressure switches
• Air temp switch
• Evaporator sensor
• Bad clutch electromagnet
• Poor electromagnet ground
• Broken or damaged wire
• Bad relay or fuse
o Mechanical
• Worn clutch surface
• Improper clutch air gap
• Bad compressor valves
• Bad compressor head gasket
• Bad compressor rings
• Broken compressor crankshaft
• A noisy compressor may be an indication of internal damage
6. High, low-side; normal, high-side
o Defective expansion valve
• not a problem on orifice tube systems
• Caused by the valve sticking fully open
• Sensing bulb may not be contacting the evaporator or outlet tube
• Make sure bulb is making good contact and that it is wrapped with cork tape to insulate it
o Defective heater control valve
o If valve is stuck open, hot coolant will enter the heater core and raise the temperature of the incoming air
o A sign of this condition is the A/C not getting cool enough
o Improper air blend door operation
o In systems without heater control valves
o If door is stuck in the “hot” position, all incoming air will pass through the heater core and the temperature will be raised
7. High, low-side; high, high-side
o Air in the system
• Look for bubbles in the sight glass if available
• Must recover, check for leaks and recharge
o System over-charge
• Check for evaporator icing
• Must recover, check for leaks and recharge
o Too much oil
• Check to see if anyone has added oil recently
• Only re-add what was removed when servicing the system
o Condenser fins plugged
• Visual inspection will verify
• Clean w/ water – opposite direction of flow if possible
• Do not use compressed air close to fins
o Defective cooling fans
• Check electrical connections and switches
• Check for seized motor
• Proper cooling at highway speeds, but poor cooling at lower speeds is an indication of inoperative fans
o Engine over-heating
• Low coolant
• Slipping belts
• Plugged radiator
• Bad water pump, thermostat or radiator cap
• Too much timing advance
o Incorrect or contaminated refrigerant
• mixing refrigerants causes a difference in expansion rates
• incorrect oil can block system and cause component failure
• system must be recovered, flushed and recharged
System Lubricants
• Lubricate the compressor’s moving parts
• Lubricate the expansion valve
• Provides a barrier to keep refrigerant from leaking out of the rubber hoses (R12)
• Refer to manufacturers specifications for oil type and amount when replacing parts or servicing the system
• R12
o Mineral Oil
o Polyol Ester (POE) – Ester Oil
• R134a
o Polyalkylene Glycol (PAG)
o Polyol Ester (POE) – Ester Oil
AT 213
Chapter 11: Retrofitting
Theories of Retrofitting
• Inexpensive
o Replace system o-rings and seals
o Replace mineral oil with ester oil
o Change service fittings over to 134a
o Evacuate and charge the system
o New label indicating R134a has been installed
• Costly
o Replace system o-rings and seals
o Replace compressor
o Replace receiver-drier or accumulator
o Replace orifice tube
o Replace all rubber lines
o Replace mineral oil with ester oil
o Change service fittings over to 134a
o Flush system components
o Evacuate and charge the system
o New label indicating R134a has been installed
• Factors to consider
o Climate
o Amount of use
 134a runs at higher pressures
o Quality of the operation before the retrofit
• Flushing the system
o Should it be done?
o When?
o Always go with manufactures recommendations
• Factors to consider
o May plug inlet screens
o Flush will remain in low areas such as the evaporator and accumulator
o Individual component flushing is the best method
o System oil must be replaced
• Refrigerant options
o 16 options
o 10 are EPA approved (including R134a)
o 4 do not require barrier hoses
 Freeze 12
 Free Zone
 Iknon-12
 FRIGC FR-12
o Service fittings must be changed and a high-side cut-off switch should be installed if the system does not already have one
o R134a is the best alternative
 80-90% of R12 capacity
 Barrier hoses must be installed
Retrofitting Procedure
• Purity Test
o Check for contaminants in the system
• Leak Test
o Visually inspect for damaged hoses or components in the A/C system
o If system still has refrigerant, check for leaks with an electronic leak detector
o If system is discharged, add 1 lb of refrigerant and dye to the system
o Check for leaks with a black light and electronic leak detector
• Performance Test
o Connect manifold gauges and document pressures and cabin temperature
o Visually inspect system while operating
o Listen for noises at the compressor, indicating a problem
o Visually inspect area between the condenser and the radiator for build-up of foreign material
• Recover Refrigerant
o Use recovery and evacuation machines to remove refrigerant
o Measure any oil removed from the system
• Compressor
o Remove compressor and drain the oil
o Rotate the compressor shaft to remove as much of the old oil as possible
o New oil must be installed that is compatible with R134a
o Replace O-rings with neoprene seals
o Compressor may have to be replaced
• Orifice Tube/Expansion Valve
o Remove and inspect the inlet screen for debris
o If plugged, replace the tube or valve with one rated for R134a
o If system has a block valve, remove and inspect
• Receiver-drier/Accumulator
o Replace with a new part compatible with R134a
• Even if desiccant is compatible with R134a, moisture will enter the system upon servicing and should therefore be replaced
o Must be installed last in the system
• Flush Components
o Only flush if contaminants are found in the system or the compressor has failed
o If component is removed, flush in the reverse direction of refrigerant flow
o If component is not removed, flush from top to bottom
o Finish by blowing air through the component to remove flush solution
• Hoses, lines and Seals
o Check condition of hoses and lines
o Replace older hoses that do not have a barrel crimp fitting with barrier hoses
o Non-barrier hoses may be used, but it is not recommended
o If hoses are being replaced, it may be a good time to install an in-line filter on both the high and low-side lines
o Lubricate all O-rings with silicone lube before installing
o If sealing washers are used, do not lubricate them
• System Lubrication
o Replace mineral oil with Ester oil
o Ester oil works well with R134a and does not cause problems if any residual mineral oil is left in the system
o Replace with manufacturer recommended amount
• Service Valves
o Remove Schrader valves and install new R134a valves over the old fittings
o A saddle clamp valve may be installed on a metal line if clearance will not allow the new fitting to be installed over the old one
• High-pressure Cut-off Switch
o Must be added to the system if one does not already exist
o May be installed over the old R12 service port
o If a clutch cycling pressure switch is used, one may consider changing it
• Switch is calibrated to cycle the clutch at slightly lower temperatures
• Evacuate System
o Connect machine and evacuate for 10 minutes
o Close valves and monitor gauges to check for leaks
o Continue evacuating for a minimum of 45 minutes
• Charge System
o Use retrofit recommended amount of refrigerant to charge
o If not info is found, start with 80% of R12 capacity and check performance
o Add additional refrigerant in 0.2 lb increments until pressures and cabin temperature are adequate
• Performance and Leaks
o Check pressures and cabin temperature, and compare to readings before the retrofit
o High-side pressure may be higher than previously recorded
o If more than 100 psi higher, there may be a blockage in the system, inadequate air-flow, or an over-charge of refrigerant
o An additional fan may need to be added to reduce condenser temperatures
o If high condenser temperatures still exist, a larger condenser may be required
o Check for leaks to insure system is sealed and repairs are correct
• Remember service fittings and pressure switches
• Conversion Label
o Place a new identification label over the old R12 label and record amount of refrigerant and oil used in the system
o If space allows, note all components and seals replaced
AT 213
Temperature & Pressure
Evaporation
Heat, Radiation, Conduction, Convection
• Radiation
• Conduction
• Convection
Humidity
• The amount of moisture in the air compared to the total amount it is capable of holding
Air Movement & Windchill
• Air movement efficiency
• Wind Chill
Cooling System Testing
• Radiator Cap
o Pressure Test
o Vacuum relief
o Worn, cracked or swollen rubber seal
• Radiator
o Visual Inspection
o Pressure Test
o Input & output temperatures (coolant flow)
o Inspect overflow tank and hoses
• Thermostat
o Opening temperature
• Sensors
o Temperature gauge sending unit and gauge operation
o Cooling fan switch operation
o Computer engine coolant temperature sensor
• Fans
o Electric fan operation (on/off temperatures)
o Fan belts, pulleys & tensioners
o Clutch fan operation
• Water pump
o Inspect bearing
o Check for leaks
• Hoses
o Look for swelling or bulges
o Check for cracks or kinks that could cause restrictions
o Check hose clamp areas for leaks and tightness
o Excessively hard or soft hoses should be replaced
• Antifreeze/Coolant
o Visually check for dirt or contamination
o Check freeze point (Hydrometer)
o Check condition of corrosion inhibitors (PH strip)
• Heater Core
o Visual inspection for leaks
o Heater valve operation
• Internal Combustion Leaks
o Dye test to check for combustion gasses
Chapter 1: Safety
Clean Air Act & Certification
• Began in 1990
• Restricts Ozone depleting elements in A/C refrigerants
• By 1992, R12 was only sold to certified technicians
• R12 was stopped being manufactured at the end of 1995
• EPA works closely with the CAA to enforce laws and set up certification standards
o ASE
o Mobile Air Conditioning Society (MACS)
Refrigerant Safety
• High pressures in storage containers and A/C systems can cause severe injuries
• Temperature effects pressure
• Explosion can occur if pressures are exceeded
• Fluid pressure or Hydrostatic Pressure can penetrate the skin
• Refrigerant in the eye can cause freeze the eye and cause blindness
o Don’t rub eyes
o Flush with cool water
o Cover eye and seek medical attention
• Refrigerant on the skin can cause frostbite
• Excessive refrigerant in the atmosphere in confined spaces can cause drowsiness or unconsciousness because it reduces the oxygen
• Refrigerant that comes in contact with an open flame or hot surface creates a toxic gas called Phosgene
o Safety Rules
 Never heat refrigerant above 125 degrees
 Keep refrigerant away from high heat or open flame
 Always wear eye protection (face shield recommended)
 It is illegal to release refrigerant into the atmosphere (R12)
 Never mix refrigerants
 Use only DOT approved containers and properly label them
• Approved tanks have burst valves to prevent explosion
 Work in a well ventilated area
Antifreeze/Coolant
• Four primary characteristics of antifreeze/coolant
1. Freeze protection
2. Boil protection
3. Corrosion prevention
4. Heat transfer
• Two main types of antifreeze/coolant
o Ethylene Glycol-based (EG)
o Propylene Glycol-based (PG)
 Standard (2-3 years; 30,000-45,000mi)
 Extended Life (5-15 years; 100,000-150,000 mi)
 Prevents corrosion build-up
 Prevents build-up of hard water deposits
 Raises boiling point
 Lowers freezing point
 Draws heat away from internal parts through a “heat-sink” effect
o Electrolysis
 Build-up of voltage in the cooling system (.3 volts or higher)
 Causes erosion of metal and gaskets
 System must be flushed and coolant replaced
 Never mix standard and extended life coolants
o Recommended Mix
 50/50 (-34 degrees freeze point)
 60/40 (-54 degrees freeze point)
Hazardous Material Safety
• Antifreeze/coolant must be disposed of properly
o Causes kidney damage if ingested
• Refrigerants must be properly labeled and stored in DOT approved containers
• Refrigerants marked with “CI” or “F” have Halogens in them and should be considered toxic. Keep away from open flame or hot surfaces and conditions
AT213
Heating & Cooling
Cooling System Operation
• Conduction
• Convection
Coolant Flow
• Standard Flow
• Reverse Flow
Radiators
• Construction
o Tanks
o Oil cooler
o Tubes and fins
o Cores (2 core, 3 core, 4 core, etc.)
• Design
o Down Flow
o Cross Flow
• Radiator Failure
o Leaks in the core from physical abuse
o Leaks in the core from corrosion or electrolysis
o Leaks between the core and tank
o Cracked or damaged tank
o Leaking transmission or engine oil cooler inside the tank
o Damaged fins
o Plugged fins from foreign material
o Plugged tubes/fins from corrosion build-up
• Radiator Cap & Overflow/Expansion Tank
• System Servicing
o Visually inspect for leaks, external damage of radiator and recovery tank
o Visually inspect for corrosion build-up in radiator core
o Pressure test & inspect cap
 Potential problems when a cap fails
 Inspect sealing surface of cap on the radiator neck for nicks or damage
o Inspect radiator shroud for damage and proper mounting
 Potential problems of a non-functional shroud
 Can increase cooling up to 30%
o Bleed air from system after adding coolant or servicing
 Many systems include air bleeds
 May have to loosen a hose at the highest point in the system
Water Pumps & Coolant Passages
o Coolant Passages
o Siamese cylinders
o Expansion Plugs
 Expansion plugs are not freeze plugs. These plugs are not designed to protect against a cracked casting in the event of freezing coolant
 Expansion plugs often rust through or leak from corrosion build-up and rust in the cooling system
 When servicing expansion plugs, high quality case sealer should be used on the plug and block surfaces before installing (do not use silicone)
o Reverse Flow Theory
• Water Pump
o May be driven by a drive belt or timing belt
o Circulates the coolant through the block and radiator
o Impeller
• System Servicing
o Check pump shaft for loose bearing if accessible
o Inspect drain hole for signs of leaking
o Inspect expansion plugs for signs of leaking
o Pressure test system to inspect for leaks
o When replacing pump:
 Inspect cooling system for contamination or foreign material that could cause new pump failure
 Compare new and old pump, including the impeller fin direction
 Inspect mounting area of pump for erosion or damage
 Take care when using sealer not to plug cooling passages
 Replace timing belt driven pumps when servicing the timing belt
 Do not over tighten belts causing premature bearing failure
Thermostats
• Operation
• Types
o Solid Expansion
o Bimetallic
o Bellows-type
• Service
o Quick and severe overheating may be caused by a stuck-closed thermostat
o An engine that never reaches normal operating temperature may be caused by a stuck-open thermostat
 Note temperature gauge
 Low heat output in passenger cabin
 Poor fuel economy
 Failed emissions
 Check-engine light due to delayed closed-loop
o Check opening temperature by measuring heat on both sides of the thermostat
Heating & Cooling (cont)
Fans & fan Assemblies
• Airflow can make up to a 30% difference in cooling system capacity
Fan Shrouds
• Directs all air movement through the radiator for more efficient cooling
Fans
• Ridged Fans
• Flexible Fans
• Clutch Fans
 Non-thermal
 Thermal
 Thermal clutch fans allow a wider RPM range for maximum efficiency and minimal horsepower loss
 Clutch fans allow for smaller water pump pulleys to be installed, increasing coolant flow, without losing horsepower to excessive fan speeds
• Electric Fans
• Fan Service
 Visually inspect fan blades for cracks, looseness or missing pieces
 Inspect water pump shaft or mounting for loose bearing
o Clutch fan should not move more than 1/8th of an inch
 Inspect clutch assembly for leaking silicon, lock up, or free-wheeling
 Install “timing tape” on the fan blades and read fan RPM
 Inspect fan shroud and air baffles for cracks, loose mountings or broken and missing pieces
 Check electric fans for seized or damaged motors
 Test thermostatic switches for proper operation
 Check operation of A/C bypass circuit
Belts & Hoses
• Belts
o V- Belts
 V belts are measured in pitch and width.
 Pitch
 Width
o Serpentine Belts
 One belt drives all the accessories
o Belt Service
 Cracks
 Glazing
 Oil contamination
 Stretch
 Pulley wear
 Pulley Alignment
 Belt Tension
 Tensioner operation
 Proper belt routing
 Checking for belt noise
• Hoses
• Servicing
o Look for kinks in hoses that could cause restrictions or hose failure
o Check for hard or brittle hoses due to excessive heat
o Check for soft or swelling hoses due to oil contamination
o Check for cracks in the hose due to stress or electrolysis
 Electrolysis cracks from the inside out
 Cracks are usually seen an inch or two from a metal mounting
 Green residue at the hose ends may be a sign of internal break-down
o Check for stretched hoses due to broken motor mounts or wrong application
o Cut hoses off when removing them to avoid damaging other components
o Don’t over tighten hose clamps
 Over tightened clamps can cut a hose
o Spring clamp pliers
o Hose clamps should always be placed next to the raised area of the connection for maximum holding power and reduced corrosion build-up
Heater Systems
• Heater Core
• Potential Problems
o Leaks are the most common problem w/ heater cores
 Wet carpet under the core in the interior
 Coolant on the ground under the evaporator drain
 Steam on the windshield during low speed blower operation
 Damaged inlet/outlet fittings due to improper hose service
o May become plugged from dirty coolant or contaminants
o Cold air due to low coolant level
o Engine overheating due to heater core restriction
• Heater Control Valve
 Manual shut-off valve
 Cable operated valve
 Vacuum operated valve
 Thermostatic control valve (electric solenoid)
Engine Overheating
• Low coolant
• Stuck closed thermostat
• Restricted radiator (internally)
• Restricted radiator fins (externally)
• Restricted water jackets in block or head
• Damaged water pump impeller
• Broken or missing fan shroud
• Plugged heater core
• Faulty clutch fan
• Faulty fan switch (electric fan)
• Seized electric fan motor
• Plugged exhaust
Cooling System Additives
• Stop-leak
o Good or bad?
o When to use?
Cooling System Flushing
• Without Flush Machine
o May use an additive to loosen up contaminants
o Drain radiator and block
o Fill with water and warm to operating temperature
o Drain radiator and block again
o Fill with water and run engine to operating temperature again
o Drain radiator and block
o Fill system with 50/50 mix of coolant and water
o Turn on heater and run engine to operating temperature
o Bleed any air from the system
o Verify that no leaks exist
o For a more extensive flush, remove the thermostat and reverse flush the block with water until exiting fluid is clean. Reinstall thermostat and fill system
• With Flush Machine
o Drain radiator
o Siphon coolant from recovery tank
o Connect flush machine between upper radiator hose and radiator
o Fill flush machine with water
o Cycle machine to fill the radiator with water
o Install the radiator cap and start the engine
o Recover the old coolant until clear water comes out
o Stop vehicle and fill flush machine with 50/50 coolant mix
o Cycle machine to fill system with new coolant
o Relieve system pressure, remove radiator cap and lower coolant level below upper radiator hose
o Disconnect the machine and reconnect upper radiator hose
o Top off radiator and recovery tank levels
o Run vehicle with the heater on and check for leaks or air in system
AT 213
A/C System Components
A/C System Operation
• Theory
o When air or liquid is compressed, it is heated by the energy of compression
o The temperature can then be lowered by cooling through a radiator
o When cooled, if the liquid or air is then brought back to atmospheric pressure, the temperature will significantly drop
o Automotive air conditioning works on this principle
A/C Components
• Compressor
o Circulates the refrigerant through the system
o Raises the pressure of the refrigerant from 20 psi to 220 psi
o reed valves
o service valves
 R12
 R134a
 Schrader valve
• Front seated
o Clockwise – all the way in; valve closed; gauge line closed
• Back seated
o Counterclockwise – all the way out; valve open ; gauge line closed
• Mid-position
o Compressor lines open; gauge line open
• Condenser
o Removes the heat from the compressed refrigerant
o Located in front of the radiator
• Serpentine flow –
• Parallel flow –
• Receiver-Drier
o A storage tank for liquid refrigerant
o Used on systems with an expansion valve between the high and low sides
• Accumulator
o Located on the suction side of the system (big line)
o Holds excess liquid refrigerant to allow only vapor to travel to the compressor
o desiccant bag
• Expansion Valve
o Separates the high and low side
o Used in systems with receiver-driers
o Block Valves –
• Orifice Tube
o Separates the high and low side
o Used in systems with an accumulator
• Evaporator
o Located inside the vehicle in the air ducting
o Receives low pressure liquid refrigerant through the expansion valve or orifice tube to cool the vehicle interior
o Flooding
o Starving
• Lines & Switches
o May be solid steel, aluminum or copper
o Some are high pressure rubber with crimped fittings
o Early style rubber lines for R12 may not be compatible for R134a
 R134a contains smaller particles in its composition which can penetrate older lines without a nylon barrier
o Hoses on vehicles made prior to 1992 should be replaced when retrofitting to R134a
• Suction Line
• Discharge Line
• Liquid Line/High Pressure Line
• Pressure Switches
o High side
o Low side
A/C Circuit & Operation
• Expansion Valve System
1) Compressor draws in low pressure vapor
2) High pressure vapor leaves the compressor and goes to the condenser
3) High pressure vapor changes to high pressure liquid as it cools
4) High pressure liquid travels to through the receiver-drier where moisture is removed and only high pressure vapor is allowed out
5) High pressure vapor travels to the expansion valve where it is metered out and lowers the pressure
6) Low pressure liquid travels from the expansion valve to the evaporator
7) The evaporator picks up heat from the air traveling across it and carries it back to the compressor
8) Cycle repeats
• Orifice Tube System
1) Compressor draws in low pressure vapor from the accumulator
2) High pressure vapor leaves the compressor and goes to the condenser
3) High pressure vapor changes to high pressure liquid as it cools
4) High pressure liquid travels through the orifice tube where it is metered out and pressure is lowered
5) Low pressure liquid travels from the orifice tube to the evaporator
6) The evaporator picks up heat from the air traveling across it and carries it to the accumulator
7) The accumulator traps liquid refrigerant and only allows vapor to exit to the compressor – also removes moisture from the system
8) Cycle repeats
AT 213
Chapter 6: System Service & Testing
Refrigerant Contamination
• Identifier
o Tests refrigerant for purity
o Must be at least 98% pure
• Sealant Contamination
o Seal sweller
o Stop leak
• Air Contamination
• Causes:
• Moisture Contamination
• Causes:
• Vacuum should be applied for 20-30 minutes and should hold when the pump is turned off for 5-10 minutes without bleeding off
• If excessive moisture is found in the system, the receiver-drier or accumulator should be replaced
Leak Detection
• Soapy water
• Visible Dye
• Black-light Dye
• Electronic Halogen Leak Detector
o A small hole drilled into the evaporator box allows access to detecting leaks in the evaporator core
Moisture & Removal
• Moisture
o Refrigerant reacts with water to form hydrochloric acid.
 The acid is very corrosive and damages all metal parts including copper, aluminum and steel
o Maximum allowable moisture content in the A/C system is 10 ppm
 One drop of water in a 2 lb system equals 60 ppm (6 times allowable)
 Preventing Moisture
• Moisture Removal
o Achieved by using a vacuum pump
o Pump is connected to both the high and low pressure lines of the system through the service valves
o Vacuum lowers the boiling point of water and causes it to boil
o The vacuum pump removes the moisture in the system in a vapor state
o 25-30 inches of vacuum should be maintained on the system for 20-30 minutes
o The pump should then be turned off and the system monitored for 5-10 minutes to see if vacuum drops off
 A loss of vacuum indicates a leak in the system
o If the system checks out ok, it is now ready for charging
Recovery & Recycling
• Recovery
o The removal of any refrigerant from the system to be stored and not reused
 Make sure all valves are turned off on the tank and gauges
 Connect hoses to the high and low sides
 Connect yellow hose to the machine inlet (if applicable)
 Open the valves for the tank and gauges
 Turn on the machine and push the recovery switch
 Machine will stop when the system is recovered
 Drain the oil into the container and measure for recharging
 Turn off the tank and gauge valves and disconnect
• Recycling
o The process of removing moisture and foreign material from the recovered refrigerant to be reused in the A/C system
 At least 8 lbs must be in the recovery tank
 Open both valves on the recovery tank and turn on the recycling switch
 Operate until the sight glass indicates that the refrigerant is clean
 Bleed any air out of the tank as necessary
 Turn off the recycling switch and both tank valves
A/C System Performance Checks
o Belt tension & Condition
o Clutch Operation
o Is the clutch cycling on?
o Does the clutch slip when engaged?
o Is there oil or dirt on the clutch?
o A slipping clutch could be caused by improper air gap, contamination to clutch surface, or voltage problems at the clutch coil
o Does the clutch rapidly engage and disengage? (low charge)
o Electric Fan
o Blower Motor
o Cabin Air-flow
o Sight Glass (if applicable)
o Is it clear?
o Are there bubbles when the system is operating? (air)
o Is there foam? (low charge)
o Is there streaks? (no liquid refrigerant; low charge)
o Low-side Line
o Is it cold?
o High-side Line
o Is it hot?
o Leaks
o Damaged tubes or hoses
o Damaged fittings or line switches
o Leaking Schrader valves
o Oil around fittings or O-rings indicating a leak
AT 213
Chapter 7: The Refrigeration System
System Charging
• Adding new or recycled refrigerant to the A/C system
• With Recharging Station
o Look up system requirements for refrigerant
o Insure all valves are closed and connect a manifold gauge set or the machine hoses to the high and low sides of the system
o Turn on the machine and input vacuum time
o Input amount of refrigerant to be used
o Open both manifold valves and both tank valves
o Start vacuum process and allow to pull for a minimum of 20 minutes
o When vacuum is complete, monitor for 5-10 minutes to insure that vacuum holds
o If vacuum holds, begin charging
o When charging is finished, close all hand valves
o Start vehicle, turn on the A/C and check pressures and cabin temperature
o If additional refrigerant is needed, use the “add” feature to add an additional 0.2 lbs of refrigerant at a time, checking the system after each addition
o If pressures and temperature are ok, disconnect hoses and turn off the machine
o Replace service valve caps
• Without Recharging Station
o Look up system requirements for refrigerant
o Insure all valves are closed and connect a manifold gauge set to the high and low sides of the system
o Connect the yellow service hose to a vacuum pump
o Pull vacuum on the system for a minimum of 20 minutes
o When vacuum is complete, close both hand valves and monitor for 5-10 minutes to insure that vacuum holds
o If vacuum holds, disconnect service hose and connect to refrigerant tank or individual cans
o Purge air out of the service line by cracking the fitting where the yellow hose connects to the manifold set
o If refrigerant is introduced in a vapor state, both high and low side valves may be opened
o If refrigerant is introduced in a liquid state, only the high side valve should be opened
o Add the system required amount of refrigerant to the system
o Close both hand valves on the manifold gauge set
o Start engine, turn on the A/C and monitor gauge pressures and cabin temperature
o Add additional refrigerant if needed
o When pressures and temperature are ok, turn off vehicle and disconnect hoses
o Replace service valve caps
o (Note: If refrigerant is to be added when the vehicle is running, only the low side is to be opened and the refrigerant tank or can should not be inverted. Inverting the can will allow liquid refrigerant into the compressor and may cause damage)
Defective Components
• Evaporator
o Plugged core; dirt or debris in the fins
o Cracked or broken evaporator case
o Leaking seal or o-ring
• Compressor
o Noise
o Seizure
o Leaking seals or gaskets
o Low suction from a low charge or restriction in the low-side line
o High suction and low output caused by defective valves or gaskets
• Condenser
o Leak from physical damage or corrosion
o Internal restriction from damaged tube
o External restriction from dirt or debris in the fins
• Orifice Tube
o Restriction from a clogged screen
o Restriction from a broken tube
• Expansion Valve
o Restriction from a clogged inlet screen
o Stuck open or closed valve
o Defective sensing bulb or bulb that is not making contact with the evaporator
System Diagnosis
1. Normal Operation
o Low-side 15-35 psi
o High-side 160-220 psi
o Cabin air temperature 35-45 degrees
o Compressor cycles normally
2. Low, low-side; normal to low high-side
o Inoperative or out-of-adjustment thermostat
• Evaporator icing caused by a stuck-on compressor clutch or an expansion valve sensing bulb that is not contacting the evaporator
o Low-side restriction
• Check along the low-side lines for temperature; should be cool to cold between the metering device and the compressor; warm spots indicate a restriction
o Plugged orifice tube or expansion valve screen
• Check along the high-side lines for temperature; should be warm from receiver-drier or condenser outlet to expansion valve or orifice tube; cold spots indicate a restriction
• Turn off A/C for 10 minutes and then turn back on; a restriction will show abnormal gauge readings immediately
o Excessive moisture in the system
• Metering device inlet is very cold due to freezing moisture
• Turn off A/C for 10 minutes and then back on; if moisture is the problem, gauge readings will be normal for a few minutes before reading abnormal again
• Receiver-drier or accumulator must be replaced
o Low refrigerant charge
• If both gauges read low, system may be low on refrigerant
3. Very low, low-side; low high-side
o Clogged inlet screen
• Compressor is tying to pull refrigerant, but can’t
• Low-side may even show vacuum
o Defective valve or tube
• A broken orifice tube can cause a restriction
• Expansion valve may not be opening properly
o Sensing bulb may be defective
o High-side restriction
• This condition will cause a high reading on the high-side gauge
o Excessive moisture in the system
• Causes corrosion and rust particles to form that may plug the system
4. Low, low-side; high, high-side
o High-side restriction
• The closer to the compressor, the higher the pressure
• Condenser, orifice tube, receiver-drier, etc.
• Check for temperature changes in the line
5. High, low-side; low, high-side
o Refrigerant not circulating
o Electrical
• A/C power switch
• Pressure switches
• Air temp switch
• Evaporator sensor
• Bad clutch electromagnet
• Poor electromagnet ground
• Broken or damaged wire
• Bad relay or fuse
o Mechanical
• Worn clutch surface
• Improper clutch air gap
• Bad compressor valves
• Bad compressor head gasket
• Bad compressor rings
• Broken compressor crankshaft
• A noisy compressor may be an indication of internal damage
6. High, low-side; normal, high-side
o Defective expansion valve
• not a problem on orifice tube systems
• Caused by the valve sticking fully open
• Sensing bulb may not be contacting the evaporator or outlet tube
• Make sure bulb is making good contact and that it is wrapped with cork tape to insulate it
o Defective heater control valve
o If valve is stuck open, hot coolant will enter the heater core and raise the temperature of the incoming air
o A sign of this condition is the A/C not getting cool enough
o Improper air blend door operation
o In systems without heater control valves
o If door is stuck in the “hot” position, all incoming air will pass through the heater core and the temperature will be raised
7. High, low-side; high, high-side
o Air in the system
• Look for bubbles in the sight glass if available
• Must recover, check for leaks and recharge
o System over-charge
• Check for evaporator icing
• Must recover, check for leaks and recharge
o Too much oil
• Check to see if anyone has added oil recently
• Only re-add what was removed when servicing the system
o Condenser fins plugged
• Visual inspection will verify
• Clean w/ water – opposite direction of flow if possible
• Do not use compressed air close to fins
o Defective cooling fans
• Check electrical connections and switches
• Check for seized motor
• Proper cooling at highway speeds, but poor cooling at lower speeds is an indication of inoperative fans
o Engine over-heating
• Low coolant
• Slipping belts
• Plugged radiator
• Bad water pump, thermostat or radiator cap
• Too much timing advance
o Incorrect or contaminated refrigerant
• mixing refrigerants causes a difference in expansion rates
• incorrect oil can block system and cause component failure
• system must be recovered, flushed and recharged
System Lubricants
• Lubricate the compressor’s moving parts
• Lubricate the expansion valve
• Provides a barrier to keep refrigerant from leaking out of the rubber hoses (R12)
• Refer to manufacturers specifications for oil type and amount when replacing parts or servicing the system
• R12
o Mineral Oil
o Polyol Ester (POE) – Ester Oil
• R134a
o Polyalkylene Glycol (PAG)
o Polyol Ester (POE) – Ester Oil
AT 213
Chapter 11: Retrofitting
Theories of Retrofitting
• Inexpensive
o Replace system o-rings and seals
o Replace mineral oil with ester oil
o Change service fittings over to 134a
o Evacuate and charge the system
o New label indicating R134a has been installed
• Costly
o Replace system o-rings and seals
o Replace compressor
o Replace receiver-drier or accumulator
o Replace orifice tube
o Replace all rubber lines
o Replace mineral oil with ester oil
o Change service fittings over to 134a
o Flush system components
o Evacuate and charge the system
o New label indicating R134a has been installed
• Factors to consider
o Climate
o Amount of use
 134a runs at higher pressures
o Quality of the operation before the retrofit
• Flushing the system
o Should it be done?
o When?
o Always go with manufactures recommendations
• Factors to consider
o May plug inlet screens
o Flush will remain in low areas such as the evaporator and accumulator
o Individual component flushing is the best method
o System oil must be replaced
• Refrigerant options
o 16 options
o 10 are EPA approved (including R134a)
o 4 do not require barrier hoses
 Freeze 12
 Free Zone
 Iknon-12
 FRIGC FR-12
o Service fittings must be changed and a high-side cut-off switch should be installed if the system does not already have one
o R134a is the best alternative
 80-90% of R12 capacity
 Barrier hoses must be installed
Retrofitting Procedure
• Purity Test
o Check for contaminants in the system
• Leak Test
o Visually inspect for damaged hoses or components in the A/C system
o If system still has refrigerant, check for leaks with an electronic leak detector
o If system is discharged, add 1 lb of refrigerant and dye to the system
o Check for leaks with a black light and electronic leak detector
• Performance Test
o Connect manifold gauges and document pressures and cabin temperature
o Visually inspect system while operating
o Listen for noises at the compressor, indicating a problem
o Visually inspect area between the condenser and the radiator for build-up of foreign material
• Recover Refrigerant
o Use recovery and evacuation machines to remove refrigerant
o Measure any oil removed from the system
• Compressor
o Remove compressor and drain the oil
o Rotate the compressor shaft to remove as much of the old oil as possible
o New oil must be installed that is compatible with R134a
o Replace O-rings with neoprene seals
o Compressor may have to be replaced
• Orifice Tube/Expansion Valve
o Remove and inspect the inlet screen for debris
o If plugged, replace the tube or valve with one rated for R134a
o If system has a block valve, remove and inspect
• Receiver-drier/Accumulator
o Replace with a new part compatible with R134a
• Even if desiccant is compatible with R134a, moisture will enter the system upon servicing and should therefore be replaced
o Must be installed last in the system
• Flush Components
o Only flush if contaminants are found in the system or the compressor has failed
o If component is removed, flush in the reverse direction of refrigerant flow
o If component is not removed, flush from top to bottom
o Finish by blowing air through the component to remove flush solution
• Hoses, lines and Seals
o Check condition of hoses and lines
o Replace older hoses that do not have a barrel crimp fitting with barrier hoses
o Non-barrier hoses may be used, but it is not recommended
o If hoses are being replaced, it may be a good time to install an in-line filter on both the high and low-side lines
o Lubricate all O-rings with silicone lube before installing
o If sealing washers are used, do not lubricate them
• System Lubrication
o Replace mineral oil with Ester oil
o Ester oil works well with R134a and does not cause problems if any residual mineral oil is left in the system
o Replace with manufacturer recommended amount
• Service Valves
o Remove Schrader valves and install new R134a valves over the old fittings
o A saddle clamp valve may be installed on a metal line if clearance will not allow the new fitting to be installed over the old one
• High-pressure Cut-off Switch
o Must be added to the system if one does not already exist
o May be installed over the old R12 service port
o If a clutch cycling pressure switch is used, one may consider changing it
• Switch is calibrated to cycle the clutch at slightly lower temperatures
• Evacuate System
o Connect machine and evacuate for 10 minutes
o Close valves and monitor gauges to check for leaks
o Continue evacuating for a minimum of 45 minutes
• Charge System
o Use retrofit recommended amount of refrigerant to charge
o If not info is found, start with 80% of R12 capacity and check performance
o Add additional refrigerant in 0.2 lb increments until pressures and cabin temperature are adequate
• Performance and Leaks
o Check pressures and cabin temperature, and compare to readings before the retrofit
o High-side pressure may be higher than previously recorded
o If more than 100 psi higher, there may be a blockage in the system, inadequate air-flow, or an over-charge of refrigerant
o An additional fan may need to be added to reduce condenser temperatures
o If high condenser temperatures still exist, a larger condenser may be required
o Check for leaks to insure system is sealed and repairs are correct
• Remember service fittings and pressure switches
• Conversion Label
o Place a new identification label over the old R12 label and record amount of refrigerant and oil used in the system
o If space allows, note all components and seals replaced
AT 213
Temperature & Pressure
Evaporation
Heat, Radiation, Conduction, Convection
• Radiation
• Conduction
• Convection
Humidity
• The amount of moisture in the air compared to the total amount it is capable of holding
Air Movement & Windchill
• Air movement efficiency
• Wind Chill
Cooling System Testing
• Radiator Cap
o Pressure Test
o Vacuum relief
o Worn, cracked or swollen rubber seal
• Radiator
o Visual Inspection
o Pressure Test
o Input & output temperatures (coolant flow)
o Inspect overflow tank and hoses
• Thermostat
o Opening temperature
• Sensors
o Temperature gauge sending unit and gauge operation
o Cooling fan switch operation
o Computer engine coolant temperature sensor
• Fans
o Electric fan operation (on/off temperatures)
o Fan belts, pulleys & tensioners
o Clutch fan operation
• Water pump
o Inspect bearing
o Check for leaks
• Hoses
o Look for swelling or bulges
o Check for cracks or kinks that could cause restrictions
o Check hose clamp areas for leaks and tightness
o Excessively hard or soft hoses should be replaced
• Antifreeze/Coolant
o Visually check for dirt or contamination
o Check freeze point (Hydrometer)
o Check condition of corrosion inhibitors (PH strip)
• Heater Core
o Visual inspection for leaks
o Heater valve operation
• Internal Combustion Leaks
o Dye test to check for combustion gasses
