Hello! On my 1997 SL1, it just blows hot air when I have the A/C button on. I noticed the cooling fan comes on when the A/C is on, but the actual compressor clutch doesn't engage. I thought maybe it was the relay, so I changed that and it still won't engage. I also recharged the system, and it holds pressure. One thing I noticed is, when I use a paper clip to jump across on the relay, the clutch engages and it works. The air is cold. But why would it do that? Thanks!

 

switch?

 

What is that, and where is it? I heard of a low pressure switch or something, I don't know much about A/C systems.

 

You don't seem to be getting much response to your question and I guess the reason is that the factory service manual with the schematics is pretty useless for AC problems.

All the schematics show is the voltage going to the hot terminal of the solenoid via a 10 amp fuse in the underhood fuse box. Since you jumped the hot terminal and the clutch worked, the fuse must be good.

So now the question is are you getting the proper ground or hot to the solenoid coil. The hot should be there as most of the circuits are ground seeking, that is hot all the time but looking for a ground to complete the circuit. The schematic in the FSM does not show which pin is hot, but it does say that the solenoid is controlled by the BCM (body control module).

Check for the 12v on each of the coil sockets on the underhood fuse and relay panel. If one of them has 12v, then you have a real problem. You will have to pull the underhood fuse and relay panel and hand trace the wire from the other socket all the way to the BCM, and if it is good, then I'm afraid you will need to drive with your windows down all the time.

One last trick, see if the compressor comes on with the HVAC in the full defrost (windshield only, not windshield and floor). If it comes on then, its a BCM issue.

The switch you are asking about will either be built into the compressor or located somewhere in the low pressure side hose. It could be under the dash next to the evaporator. The FSM doesn't show it, however the connector for it is at the back of underhood junction block. If you have at least 30 psi in the low side, the switch should make.

 

Could be a faulty pressure switch. If it works with the paper clip, and blows cold air, I would replace the switch. Or you can just leave the paper clip in place, and pray that the system works fine. May want to just try the paper clip for a couple hours, and see if it works later with the relay. I had a friends car that I did this with, and it now works fine after 3 years, relay, and everything intact.