AC compressor switches help

[DavsR]

Hello community! I've tried searching but cant find any specific direction on how to test the triggers for the AC compressor like the high and low switch or thermostat switch. I've refilled my system with 1.5lb of r12 and had to run a power line from battery to compressor in order to get it to work. It blows ice cold! My problem is the compressor only works with direct power and I don't know what steps to take in order to test the switches. I replaced all O rings, new drier, new expansion valve and I've cleaned out the evaporator (looked like a nest of dirt and carpet in there), I made sure the wire to the thermostat switch was connected along with the high/low switch. Please help me figure out why my compressor won't kick on with the AC button /ubbthreads/images/graemlins/banghead.gif /ubbthreads/images/graemlins/bawling.gif

 

[DavsR]

Ps I found the electric diagram for the ac system and i know the pressure switch is first to be checked then the thermostat switch but still confused on how to check voltage an proper function for these. AC diagram

 

[ktmrider]

The switches are simple NO or NC types ( Normally Open or Normally Closed ). No voltage measurement, use resistance checks.

#3 or top one is NC. #4 on back/rear of housing is NO. Check #4, hard to see and can easily be disconnected.

 

[galant651]

there is a inline dual pressure switch that you will need to check. if its not reading right the compressor wont turn on. the relay also needs to be checked, according to the diagram thats the last thing before the compressor. so check power at the relay and if you have power in and none out then its your relay.

 

[DavsR]

Thanks for the suggestions guys. Are there two relays for the AC system? I look at the fuse box over by the battery and it has two AC relays? At any rate I replaced those and the high/low switch to see if this fixes the issue. Does anyone know whether the ac temperature switch on the preasue switch can make the compressor not turn on?

 

[donniekak]

Turn the ac on, and test for power at the duel pressure switch. If there is not 12 going to that switch, there is a good chance the ac control computer is bad.

 

[DavsR]

Okay so after a month of trying to figure things out and replacing part after part I still can't get ac compressor to run! I've replaced expansion valve, conensor, drier, hi low switch and little control Box behind dash (got it at junk yard). I'm not getting 12v to hi low pressure switch. Is there any way to test controller ehind box? I'm running r12 and filled system with .8 pounds to try and get compressor to activate. I'm super frustrated and any help is appreciated. Thanks

 

[tsitalon1]

Don't know how to test it but - Try another controller box.

 

[vr4play]

The ecu is what activates the A/C clutch from pin 65. Try jumping the dual pressure switch and see if that does anything. The ecu gets it's signal from the a/c control unit pin 8 which I believe gets power from the ignition switch.

 

[Vr4junkie]

Quoting DavsR:
Okay so after a month of trying to figure things out and replacing part after part I still can't get ac compressor to run! I've replaced expansion valve, conensor, drier, hi low switch and little control Box behind dash (got it at junk yard). I'm not getting 12v to hi low pressure switch. Is there any way to test controller ehind box? I'm running r12 and filled system with .8 pounds to try and get compressor to activate. I'm super frustrated and any help is appreciated. Thanks



Have you tried connecting a wire from the battery to the A/C power line to see if the clutch is even working?

 

[DavsR]

Thanks for the help guys, I have connected a power line directly to the AC compressor and it will turn the compressor on. But it will not work by pressing the AC switch in. I have ECM link v3 and I have the AC switch logging and it never shows it turn on. The only thing I can think is that the actual AC switch on my dash doesn't work? But I haven't tried putting a volt meter to it.

 

[theevozero]

With that wiring diagram, basic knowledge and a DVOM, you should be able to figure this out in no time. All you have to do is chase power. See which side of the compressor relay is not working, the control or power side.

 

[Eaglesfly]

Bringing this back because I'm having the same issue. Was the issue ever found and resolved?