1986 grand national digital climate control

[1986grandNash]

Hi I’m making this post because I need some help on figuring out why my ac compressor won’t engage. I have power at all the wires on the ac module except the purple wire. I’m getting power at the low pressure switch. But no power at the ac relay or compressor clutch. I’ve already put a new ac relay in the car and checked the fuses and there good. Can anyone tell me what could be the issue? I posted a picture of the voltage off the wires we checked.

 

[SCOOBY DOO]

Not sure if this will help:

https://www.vortexbuicks-etc.com/ac_compressor_electrics.htm

 

[1986grandNash]

Ttt

 

[HotAirWH1]

Ttt

Do you have the schematics of the AC wiring ?

 

[TireFryer]

Do you have enough Freon in the system? If you don’t the compressor won’t kick on. Or you may need to adjust the pressure switch. It’s by the map sensor of the firewall. I think it’s a black plug with a green and blue wire

 

[1986grandNash]

Do you have enough Freon in the system? If you don’t the compressor won’t kick on. Or you may need to adjust the pressure switch. It’s by the map sensor of the firewall. I think it’s a black plug with a green and blue wire

There no Freon in the system because we a new compressor

 

[TireFryer]

There no Freon in the system because we a new compressor

That’s why. Get a can and start adding it. The compressor should start cycling and stay on eventually

 

[1986grandNash]

That’s why. Get a can and start adding it. The compressor should start cycling and stay on eventually

But I’m not getting any power at the ac relay or the plug on the compressor clutch.

 

[xlr8ngn]

I would jump the low pressure switch on the accumulator to see what happens. When you don't have a charge, the low pressure switch keeps the compressor from running without refrigerant. I would assume the compressor can run for a second and not self destruct, but IDK for sure. I would be patient, complete the AC install and charge with refrigerant and oil, then try.

 

[1986grandNash]

I would jump the low pressure switch on the accumulator to see what happens. When you don't have a charge, the low pressure switch keeps the compressor from running without refrigerant. I would assume the compressor can run for a second and not self destruct, but IDK for sure. I would be patient, complete the AC install and charge with refrigerant and oil, then try.

I tried jumping the low pressure switch and the compressor still doesn’t work. I have 12 volts at the switch.

 

[daveb7577]

Why are you trying to run the system with no refrigerant? You replaced the compressor, did you replace the accumulator also? What refrigerant are you going to use, R12 or R134? If you are going to use R134 you need to flush out the entire system of the mineral oil and add the proper amount and viscosity of PAG oil. R134 is not a drop in replacement for R12. Do not run R134 with mineral oil. Do not mix mineral and PAG oils. You will trash the entire system. Mineral oil is for R12 only. Also before you charge refrigerant you need to pull a vacuum on the system to remove the non-condensables and ensure system integrity. Again not pulling a vacuum on the system you will end up trashing the system.
If you don't do these things the system will under perform, be troublesome, and eventually die. You need to do these things before troubleshooting the control system. There's probably nothing wrong, you've skipped a bunch of stuff that have to be done first.

 

[1986grandNash]

Why are you trying to run the system with no refrigerant? You replaced the compressor, did you replace the accumulator also? What refrigerant are you going to use, R12 or R134? If you are going to use R134 you need to flush out the entire system of the mineral oil and add the proper amount and viscosity of PAG oil. R134 is not a drop in replacement for R12. Do not run R134 with mineral oil. Do not mix mineral and PAG oils. You will trash the entire system. Mineral oil is for R12 only. Also before you charge refrigerant you need to pull a vacuum on the system to remove the non-condensables and ensure system integrity. Again not pulling a vacuum on the system you will end up trashing the system.
If you don't do these things the system will under perform, be troublesome, and eventually die. You need to do these things before troubleshooting the control system. There's probably nothing wrong, you've skipped a bunch of stuff that have to be done first.

Yes I replaced the compressor and accumulator. I’m converting it over to r134. I’ve already flushed out the system.

 

[TireFryer]

Yeah you can try jumping the pressure switch. I used a paper clip and just turned on the ac when I wanted it lol. They’re pretty cheap if that helps you narrow it down at all.

 

[1986grandNash]

Yeah you can try jumping the pressure switch. I used a paper clip and just turned on the ac when I wanted it lol. They’re pretty cheap if that helps you narrow it down at all.

I already tried jumping the low pressure switch it still doesn’t engage

 

[TireFryer]

What mode on the climate are you using? I think you have to do auto mode. I have the digital climate too

 

[salvageV6]

If the dark green wire has +12 on it jumped from the light blue wire on the connector of the pressure cycling switch, assuming no freon but controls ON, you should see that +12 on the relay terminal D the light blue wire. Check the ECM/SOL fuse that powers the relay and the ECM grounding wire. However that light blue wire goes through C497 a 4 cavity connection over by the pass. fender near the antenna and it's known for corrosion so check that spot first.

 

[1986grandNash]

Ok. I have no power at the relay. I checked the ecm/sol fuse, it’s good. Where can I find the ecm ground wire? And I’ll try and look for that light blue wire by passenger fender.

 

[salvageV6]

At the A.C. cut out relay connector, pink/blk wire goes to ecm/sol fuse, the wire has +12 on it with key in RUN, BULB TEST, or START.
Light blue wire should have the same +12 on it as found at the accumulator jumped cycling switch, +12 when A.C. is ON at the control head not sure of those conditions with C68 A.C. but you said you had power there at the cycling switch, make sure it stays jumped at the cycling switch connector to test further along towards the compressor for power.
The Dark Green wire is the switched output of the relay and should have +12 on it when the relay is ON assuming the light blue has +12 on it.
The Dark Green with Yellow stripe wire is the ECM ground control wire for the relay, when grounded I believe the compressor runs. When the ECM removes the ground and the relay shuts off so does the A.C. compressor and the dark green wire loses +12 volts.
I believe this is the connector the blue wire goes through pictured.

 

[1986grandNash]

I still haven’t figured out my problem smh

 

[1986grandNash]

I found my issue. Ac compressor clutch plug wasn’t receiving a ground. I tapped into the black wire on the plug and grounded it to ac bracket. Thanks again for everyone help!