Condenser fan operation

[Who]

1989 7mgte (turbo 3 condenser fans)
Do the condenser fans turn on if the AC is off, but the ambient temp or water temp reaches the sensor trip points. Remember the ac is off.
Thanks

 

[Poodles]

The aux fans on the side of the radiator? Yep, when my car used to get too hot they would trip on.

If they're turning on, you're on the boarderline of overheating IMHO (since my cooling system upgrades they haven't come on)

 

[skipbarber]

yea, my car doesnt have functional AC anymore, but the small fans kick on when the car is left idling for a while.

 

[Nick M]

You can hard wire the high pressure switch to a toggle switch inside the car. Just remember to turn it off. I did it once.

 

[Who]

You can hard wire the high pressure switch to a toggle switch inside the car. Just remember to turn it off. I did it once.

From the schematics provided i can ground pin 1 on the high pressure switch(22) or ground the wire on water temp switch #3 (28) and activate fan relay #1(21) and fan relay #2(27).

I also see that fan relay #3 (33) can only work if fan relay #2 (27) is activated or closed allowing the current to flow to it.

Fan motor #1(23) & Fan motor #2(26) are only wired to Fan relay #1(21) and can be activated by water temp switch #3(28) when the ground circuit is completed by the water temp switch #3(28)

The high pressure switch (22) is on the passenger side coolant line closest to the firewall according to the last photo.

Pins 1 on fan relay #1 and #2 go directly to the fuse link box and through the 40 amp fuse to the battery

The current that provides the relays with the switch or current to close the main switch in the relay when the ground is applied for the heavy draw of the fans comes from the gage fuse 7.5amp. This gage fuse is the same one that lights up the seatbelt lights, ect light on the dash.

Sorry about the university test question but I am trying to sort out my current paths to find a out why I have no condenser fans regardless of temp, ambient or high side pressure on the ac system.

Fuses have been checked with ohm meter.

Thanks

 

[Who]

Ok so I grounded Water temp switch #3(28) and all the condenser fans turned on. I grounded the High Pressure switch (22) and the condenser fans turned on. So now I know that I have a working, viable condenser fan circuit. Yahoo!!!

How do I test the High pressure switch (22) ??

The water temp switch did not activate the fans because the water temp never got to 212.F Thats a good thing. My cooling system is working just fine.

Does anyone know how to test the high pressure switch?

If I remove or unscrew the high pressure switch from the coolant lines do they leak out to atmosphere or is there a schrader valve that stops the leak when the switch is removed?

 

[jetjock]

Lots of ways but the easiest is to put a manifold gage set on the system then turn the AC on and block the condenser.

 

[Who]

Lots of ways but the easiest is to put a manifold gage set on the system then turn the AC on and block the condenser.

Running the ac in the middle of the day in Florida with the ambient temp 90F and no condensor fans turning on is sorta like blocking the condenser and thats why I am doing all these test.
I have bubbles in my sight glass when the compressor runs. So I went to my trusted domestic car mechanic and he put the manifold gage on the ac system. The high side kept rising and the low side kept dropping. The condenser fans never kicked in. So he tells me that the fans are not turning on, the heat on the condenser is building up causing the high side pressure to rise. The compressor kept running, the dual pressure switch never disengaged the magnetic clutch, and the condenser fans did not turn on which are activated by a separate high pressure switch. I seriously doubt that both the high pressure switch and the dual pressure switch are both faulty. I find that the high pressure switch should close/ground and activate the condenser fans at 15.5kg (220psi) or higher. The dual pressure switch closes disengaging the compressor magnetic clutch at 27kg (384psi) or higher. I wish I would of been watching those gages to see if the high pressure was high enough to set off the dual pressure switch. I guess I need to find or buy a manifold gage.

I know the pressure definitely went over 15.5kg (220psi). If I replace the high pressure switch will the system leak or is there a valve that prevents the system from going to atmosphere?

At least the mechanic was honest and told me he did not like how high the pressures were and he honestly did not know about supras and told me to hit the road, no charge, bring me back a domestic car someday.

Thanks for the help

 

[jetjock]

Well, if the pressure definitely went over 220psi and yet the fans turn on when the switch is jumpered the solution should be intuitively obvious: Replace the switch. You'll have to recover the refrigerant to do it. In such cases I usually recover then pressurize with N2 for testing. It beats vacuum by leaps and bounds. I'll put some refrigerant, usually R22, in with the N2 to make leak testing easy and cheap.

It sounds like you need a better mechanic. The refrigeration side of the system in these cars is about as typical as they get for the era. Common as dirt on domestic and foriegn cars alike. If the high side kept rising and the low side dropping there is a restiction in the system, probably a bad expansion valve or a blocked condenser. That's as close as I can come without actual numbers. Bubbles in the glass typically indicate a low charge.

And yes, buy a manifold set. Attempting any real AC work without one is basically futile.

 

[Nick M]

And a low charge indicates a small leak. When you have it professionaly serviced, they will put dye in the refridgerant. They might tell you to come back in a week, to check see if the dye is escaping.

And I never messed with all those fan controls, only the high pressure switch was jumped, and I had control of it.

 

[Who]

Well, if the pressure definitely went over 220psi and yet the the fans turn on when the switch is jumpered the solution should be intuitively obvious: Replace the switch.

Yes your absolutely right. The normal high side pressure should be between 206-213psi according to the manual. The high pressure switch should close at 220psi. Any pressures slightly above normal would close the switch and activate the condenser fan relays. It was right in front of me but I guess I was thinking about it to hard.

As far as the mechanic I sometimes think he is more of a wrench than anything else. The guy is honest, almost to a fault, thats hard to find in south Florida.

Will look for some ac manifold gages.

Thanks again,