Air conditioner electrical troubleshooting ?

[easternguy2005]

Troubleshooting the A/C on '90 GTE found the fuse but its much more.


I can't figure out where the fuse is to start. The fuse is on the schematic but I see no fuse in the footwell or mains by the battery.

Any help is appreciated.

 

[jdub]

http://www.cygnusx1.net/supra/Library/TEWD/MK3/manual.aspx?S=Main&P=032

Pages 32 & 33

 

[easternguy2005]

I think this means that if the cig lighter is working and the power antenna is working then the fuse is OK for the A/C clutch.

Where Can I find the relay for that A/C clutch.

Incidentally, R-34 pressure is good and 2 switches on high line are correct ohms. A/C light comes on on cabin control when pressed. Still not getting ANY juice coming on the wire to energize the clutch though.

 

[easternguy2005]

http://www.cygnusx1.net/supra/Library/TEWD/MK3/manual.aspx?S=Main&P=014

ok looking - any other tips are appreciated

 

[jdub]

Have you looked at this section?

http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?Section=AC&P=15

 

[easternguy2005]

Yes, I spent my day going through that. I even did the step 3 which is check the AC button. Pulled out the cabin unit and did the voltage test. You see the green light comes on when I press AC but I'm not satisfied with that.



Questions ?

When you turn the ignition on (engine not on). Turn the fan on medium, and say blow it toward your body, If you then click the AC button on ---


Does your compressor clutch then click in ?
Do your electric fans start spinning right away ?

All I get is a green light and nothing clicks or spins. The temp control works though because if I raise the temp to room temp the fan slows down and then next I hear the click for the heater relay (to let some heat core action happen)

 

[Halsupramk3]

the 25 amp fuse for the a/c clutch is in the passenger side kick panel. you can take the panel off beside the glove box and check the fuse. also if you have too much freon or too little (too high of presure or too low) the presure switches will not let the clutch engage.

you can test the clutch by unhooking the wire to the clutch at the connector and then wire 12v power directly to the clutch side of the wire. you can hear or feel the clutch engage. of course the engine is off while doing this. the a/c button on the control unit turns a relay on that supplies 12v to the clutch wire that is grounded to the a/c housing.

 

[jetjock]

^ What he said. To answer your other question the clutch should engage KOEO. You can check the CC panel and wiring (at least the wiring to the ECU) by looking for a code 51 when in diag mode. Keep your foot away from the gas pedal when doing it...

 

[sneakypete]

are the electric fans only supposed to come on with the AC? mine comes on and off all the time regardless if the AC is on. i also notice that there is no difference when i press the AC button.... if the temp is lowered, the air gets colder.
im worried that the AC is always running even in the winter, its just that i raise the temp hot
any ideas?

 

[easternguy2005]

STILL no AC and its hot outside. Took it to a shop and he called me 1/2 hour saying he can't fix it - pick the car up. Never heard that before.

Meanwhile I got a used cabin control unit from the junkyard for $10 and didn't help any.

On many (all?) new cars the AC turns on when you have the windshield defrost on and the AC button off.

The electric fans on my supra are positively controlled by the high pressure switch behind the hi/lo switch along the silver freon pipe right by where the turbo is. The one that controls the fan(s) is the one that closer to the back of the car.

I replaced the hi/lo switch and have a can pressure on the low side so the pressure is enough to complete the circuit.

Welcoming any suggestions cause this takes the "luxury" out of my supra.

 

[easternguy2005]

Yes, I spent my day going through that. I even did the step 3 which is check the AC button. Pulled out the cabin unit and did the voltage test. You see the green light comes on when I press AC but I'm not satisfied with that.



Questions ?

When you turn the ignition on (engine not on). Turn the fan on medium, and say blow it toward your body, If you then click the AC button on ---


Does your compressor clutch then click in ?
Do your electric fans start spinning right away ?


ANSWERS:

The compressor doesn't click on (or relay) when I hit the AC button which lights up.

The electric cooling fans by the radiator do not spin when the AC button is engaged. They do spin if I short the high pressure switch connectors.

I tested the clutch relay and can successfully apply juice to engage the relay and it then engages the clutch.

The blower fan works good and when I lower the automatic temp to 65 degrees it blows hard - raise cabin temp digits to 85 and the fan slows down accordingly.

Checked the thermistor ohms and its right on target.

Not sure what the amplifier does and can't find the plug that is shown in the diagram on the service manual.

 

[jetjock]

Did you check for a code 51 with the AC on like I said to? There's only one control line to the amplifier so it's easy to test. Not so easy to get to though.

 

[easternguy2005]

Did you check for a code 51 with the AC on like I said to? There's only one control line to the amplifier so it's easy to test. Not so easy to get to though.

I have the interior body panels removed (glove box etc) but don't understand code 51

Do I try and pull a code like I would from the ECM if the engine was giving problems ?

I can't locate the wire to test that you mentioned - need more description please

Thanks

 

[jetjock]

Assuming the power side of the AC circuit (10 amp AC fuse, Cig fuse, wiring, and relay) are good there are only a few things that'll prevent clutch operation. Code 51 provides a quick way of checking most of these things as well as testing much of the amplifier.

1) Jumper the diag block, same as would for checking any engine code.

2) With your foot off the gas pedal look for a normal code on the MIL. If you get a code 51 with the throttle closed stop right there because the test will be invalid. If you get a normal code proceed.

3) Key on, engine off, throttle closed, and if auto in P or N: turn the blower on any speed and press the AC switch. The button should light up and code 51 should appear on the MIL. Do that and we'll go from there.

The AC amp controls the clutch but the amp is controlled by the Heater Control Assembly, aka the CC panel. Since there are inputs on both that will keep the clutch from operating, code 51 allows us to see which of these two devices is causing the problem. Since the engine ECU (which operates the MIL) gets the signal from the amplifier if you get a 51 you'll know everything on the CC panel side is working and the problem must lie in the amp or power side of the circuirt

 

[easternguy2005]

Assuming the power side of the AC circuit (10 amp AC fuse, Cig fuse, wiring, and relay) are good there are only a few things that'll prevent clutch operation. Code 51 provides a quick way of checking most of these things as well as testing much of the amplifier.

1) Jumper the diag block, same as would for checking any engine code.

2) With your foot off the gas pedal look for a normal code on the MIL. If you get a code 51 with the throttle closed stop right there because the test will be invalid. If you get a normal code proceed.

3) Key on, engine off, throttle closed, and if auto in P or N: turn the blower on any speed and press the AC switch. The button should light up and code 51 should appear on the MIL. Do that and we'll go from there.

I did as said - ECM blinking on/off steady indicating all is well.

I click on AC and fan and the ECM doesn't change. Blinks just as it did prior. No codes. Blower fan blowing, green light indicating AC should be on at AC button.

 

[jetjock]

Assuming the button lit up the problem likely lies on the CC panel side. Check the ambient air sensor, it's near the hood latch. Or check pins 1 and 2 on connector E at the CC panel

Either that or the amp or wiring to it is bad. Only way to know is to check and see if pin 14 (green/orange wire, connector D) on the CC panel changes with the AC on. That's the output that tells the amp to become active.

 

[Halsupramk3]

if you can feel the clutch engage with 12v applied check the clutch relay for proper operation.

Did you check the 25 amp fuse in the passenger side kick panel?

That is the fuse that supplies power to the clutch that you say is not engaging. the 10amp a/c fuse gives power to the ac controls and not the clutch. you can see if you are getting power to this 25 amp fuse. your problem sounds like it would be the 25 amp fuse most likely, then the clutch relay by the fuse box, or the hi/lo presure switch if faulty. Thats in order of most likely to least.

 

[easternguy2005]

if you can feel the clutch engage with 12v applied check the clutch relay for proper operation.

Did you check the 25 amp fuse in the passenger side kick panel?

That is the fuse that supplies power to the clutch that you say is not engaging. the 10amp a/c fuse gives power to the ac controls and not the clutch. you can see if you are getting power to this 25 amp fuse. your problem sounds like it would be the 25 amp fuse most likely, then the clutch relay by the fuse box, or the hi/lo presure switch if faulty. Thats in order of most likely to least.

Well I'm going to put a section together on AC electrical after all this. Spent the weekend messing with it. Here's what I have found with help from everyone.

When Pin 7 is jumped to pin 10 on the amplifier connector the clutch locks down. So anything past the amp is good to go.

I just can't figure out what the deal is with the signal that goes from the Cabin Control to the amplifier. The link between them is 14 off the cabin control.

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=142


when I tested the amp at #2 the only input is the fan speed by different voltages.

Does anyone have experience with this ?

Still confused by this in shop manual:

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=AC&P=40




(
replaced high/low switch and system is pressurized.
Fuses LOOK OK, additionally the cig lighter works, blower works, juice to relay makes clutch come on so that comes from the 10amp fuse.

Clutch relay is under first main box behind the battery - checked and OK


)

 

[Davismj711]

Same exact problem here ^^ I am working on it today. If I discover the problem I will post it, if you find it first I will fix mine also. Good Luck !!

 

[Davismj711]

Ok, I got mine running. I had done the clutch relay test incorrectly. I switched both relays under battery out from my swap car and it is all good. Perhaps you need to replace both relays eastern, not just the magnetic clutch relay described and pictured in the manual. The power source flows into one relay and is routed via the white 4 prong plug into the magnetic clutch relay...
Hope this helps you out..