Lary Ellis (Top)

My A/C stopped working on my 96 2500. I took it in to have it fixed and everything checks out great. You can jump the relay and it works. We swapped relays with the one from my horn and no help. Relays are OK.

Technician thought it was the switch on the dash, but that checks out OK as well. I am looking now for a bad wire or possibly a PCM problem. System is charged properly and appears to be in perfect condition.

Anybody have any ideas? or experienced this problem?

scuzman00

Lary,

If the system in the dash (fan) works, but the compressor will not cycle, it could possibly be a bad low pressure switch that is a compressor lock-out feature.

Hopefully this helps.

Gary

Partsman

My boys 98 has the relay in the box under the hood and the feed terminal for the relay was dead. I just bent that terminal up pluged the relay back in and put a seperate feed with a inline fuse from the bent terminal to the stud for the box feed. I hope I am clear as mud.

Lary Ellis (Top)

Thanks, Gary and Partsman for your responses.

I can jump the low pressure switch and the compressor will come on, but since it also works when the relay is jumped, I am assuming the low pressure switch is not the problem. I did replace it last year as it had a leak in it.

I will check out the feed terminal in the relay box as suggested, possible that is my problem as well.

There was recall work done under the dash that included rewiring a portion of the blower circuit, due to overload on the ignition switch. The blower works fine but I may have to look at that real close as well.

It could be something as simple as a bad connection on the work that was performed by the dealer.........Nah they ALWAYS get it right

nitrousn

if you have to jump the low pressure switch it sure seems like that is where the problem is. did you see the pressure readings on the high and low sides?

jumping the relay and making the clutch engage is bypassing all the rest of the system andjust making the cluch work. there again you say it still does not work or cool properly.

i would get the pressures retested. its low or restricted. if you get the gauges on it and make the compressor run i would look at the low side readings. if it goes low or to a vacuum it may hace an expansion valve or metering orfice problem.

TGCTD

If you jump the relay and the clutch engages and you cool down then i would get i wireing diagram and see what you are loseing at the relay. If you jump it and it works then you have two of the four circuits working. 1. The wireing from relay to clutch is OK,because you made it work. You didn't say where you got power from. If it was from the relay,then two of your circuits are good. You either have a bad ground (possible grounded via the PCM) or the other feed wire. I will look at the wireing diagram and see if i can get more info for you. Tony

MnTom

I agree with nitrousn. If you jump the low pressure switch and it works there is either a pressure problem (low pressure) or a switch problem. By jumpering the relay all you are doing is the same as putting power to the compressor clutch itself. All that jumpering the relay did was show you that the circuit from the relay to the clutch is good. Check for continuity through the low pressure switch. If you have continuity then the switch is good. If you do have continuity, then you need to start tracing the power from the relay and work your way backwards to find the problem.
Tom

Lary Ellis (Top)

The A/C Mechanic that was working on my truck jumped from the battery to the contact side of the relay. It acts as though it is not getting a signal either from the PCM, or the ground as mentioned.

I am going to take my meter out there this afternoon and start looking it over real close. The pressures are right on the money, he ran it through it's paces while he had it hooked to the machine.

He was certain it was the switch on the dash, and told me he was stumped as to why it wasn't working. I have some diagrams here from a Haynes manual, though I need to quit fooling around and get a real manual for it

Been saying that since I bought the truck new in 96....The name Procrastinator is in use already by another member

nitrousn

QUOTE[[[[[[I can jump the low pressure switch and the compressor will come on, but since it also works when the relay is jumped.]]]]]]]]]]QUOTE

Larry you are making more work for your self. in your previous post you said the compressor runs when jumping the low pressue cut off switch. in my opinion you have already confined the problem to one of two things. a faulty low pressure switch or a low or malfunctioning system pressure wise. like i previously stated get some pressure readings and go from there. also get the readings when the compressor is jumped. not to cut your ac tech. short but i am not convinced that he knows that much. i base that on your previous posts with the jumping of the LP switch and the relay. the relay is not going to work because the pcm sees the LP switches readings. if they are ok it will allow the clutch relay to engage. you jumping the LP switch tells me the electrical part is fine and capeable of working.--- pete