I do not have any relays on my driver's side fender well, except for the heater grid relays.
Where is the A/C relay on a 1990 Dodge Diesel?

 

One more stupid question: So is the cycling switch bad if you apply ground to the brown wire coming off of the cycling switch and the clutch engages or does that mean the PCM is bad?
Thanks,
Derik Harris

 

Dark blue with orange stripe, dark blue, and brown. Dark blue is power for the circuitry inside the switch, the other two wires are the wires that the switch controls.

You don't have one. It's a '92 and '93 thing.

In your case, all that means is that the clutch works. Now if you run a jumper between the two outer wires in the cycling switch connector and the A/C works, then the cycling switch is bad.

 

Well I tried grounding out the cycling switch (3 wire) and I have nothing so for now I'm trying to eliminate the small things. I ordered up a new relay to see if that does anything for me.

Now after thinking about it and re trying the hotwiring on the compressor, the AC doesn't feel that cold, so I'm guessing I probably am low on R-12 and it isn't getting enough pressure to kick on the pressure switch. After 340,xxxkms its probably needs a recharge.

 

Thanks a lot wanna diesel, it was the cycling switch.

 

Read Jim Lane's article on bypassing the cycling switch in the sticky. His setup will take the load off the HVAC panel.

 

Yeeehaaaw, I got the A/C to work and all it cost me was one relay! I figured that I'd eliminate the small stuff first so I ordered a new relay (driver's side fender) and popped it in and bam! A/C works now. I think it needs a bit of a recharge since it isn't super cold, just cool air but it works nonetheless and I am super happy right now

 

Ok after a bit of testing I noticed that the compressor isn't cycling on and off like it should. Could I have a bad cycling switch? Also, I noticed that there is a piece of copper tubing about a 1/8th of an inch in diameter with a wire hooked to it on one end and the other that is inside one of the hoses. Its loose and I have a feeling that it shouldn't be...

Any insight?

 

It shouldn't cycle, it should run.

That tube is supposed to be loose. I have mine pulled almost all the way out so the compressor won't cycle.

 

Whaaat? I thought it should cycle or it would burn up the compressor from running constantly?

 

Nope. Cycling will kill the clutch.