AC troubleshooting Help Needed

[Rob Scariano]

I have a 99 OBS 2 door Tahoe.

The AC compressor and clutch works but only when I apply 12v manually. I've tried re-charging the system. I've tested the AC control switch, which works.

Is there anything else I can try. It worked fine one day then it all of a sudden stopped. I've changed out the relay and that didn't help. So I'm thinking that the issue is somewhere else.

Any advice would be greatly appreciated.

 

[Rob Scariano]

I forgot to add that I did check the R134a. The pressure is where it needs to be.

 

[sumo]

What about the pressure sw? What've you checked that? If it's dead its the same as reading no pressure in the system

 

[Rob Scariano]

What about the pressure sw? What've you checked that? If it's dead its the same as reading no pressure in the system

I haven't tried that yet. Is there a way to bypass it to see if that is the problem?

 

[sumo]

You can try shorting it. I believe it is 2 pin

 

[Rob Scariano]

You can try shorting it. I believe it is 2 pin

I

You can try shorting it. I believe it is 2 pin

Thanks. I'll give it a shot

 

[Rob Scariano]

I

Thanks. I'll give it a shot

I shorted the connector going to the low pressure switch. Nothing happened. The clutch only engages when I apply 12v direct to the lead that engages the clutch.

Any thoughts?

 

[sumo]

Ok hove you check fuses? I assume the light on the control panel comes on? Also check the relay. Pop in another relay or swap one from another location to see if it will work. There is also a hi press switch you can check. Make sure the connection is good there. Other possibilities could be a broken/bad connection before the relay so the system will never energize the relay. You could also have a bad control panel, or pcm. The problem sounds to be o the control side of the compressor. Something is not telling the pcm to supply ground to compete the circuit.

Since you can force the compressor on, it's not the compressor as it's always has power and ground available.

 

[Chris1stgenali]

I had a similar issue, tried swapping the relays, same thing, so I bent the prongs on the relay a little bit and put it back in, wala