Hey folks,

I bought a 2002 R50 with 80,000mi on it last week and the AC does not function. The compressor will not run. The first thing I want to check is the pressure switch. I’ve pulled the battery box and now have access to the switch, but I don’t know how to test it 😅. I’ve read that one should “jump” the pressure switch, but how is that done? The battery and air box are out of the car, so I suppose this would be a bench test…but if I remove the pressure switch from the line will all the refrigerant vacate the AC system?

Unfortunately I can’t find anything regarding the AC pressure switch in my Haynes manual.

Thanks in advance for any help!

Photo of the pressure switch:

 

If they are normal 2 terminal switches and the system is full of Freon then they should have continuity across the switch. The low pressure switch will be closed when the system is full and open to cut the signal when the Freon is low. A high pressure stitch cuts pressure when the system encounters an over pressure of Freon.

 

The AC won't work if the power steering fan has seized and blown the fuse. I'd check the fuse first. Also the compressor won't work if the freon is too low.

 

First read presure, low and high.

do u have gauges?

harbor freight has a cheap set.

YouTube for the how-to

and eye protection for the win

 

Thanks for the replies guys. I was putting the cart a bit before the horse here. I will be picking up some things from the parts store today so I can check the system pressure. What pressure range should I be seeing without the compressor running?

If there is pressure then I will double check the voltage at the relay to see if the compressor clutch coil might be an issue too.

 

There is one wire behind the alternator that goes to the clutch. Check if yours is still connected. I had to replace that, and all is working.

 

Good video if the clutch RnR is needed.

 

Fuse was all good.

I checked the AC relay you can hear it 'click' when it is connected. I also swapped the starter relay with the AC relay and the compressor wouldn't run. I checked for continuity between pin 87 on the AC relay and good and there was nothing. According to Scott Philbrook's Youtube Video " " this would indicate no continuity to the clutch coil. I will have a look at the clutch coil connector tonight to see if it is plugged in.

I picked up an AC 'recharge' kit from the local parts shop last night and hooked the gauge up to the low side of the system. It read 27psi (@17*C). Then I hooked the can up and opened the valve for a split second and the pressure went up to 33psi. Seems like nothing really went in. Anyhow, the compressor still wouldn't run after that.

Possibly irrelevant diversion: I've seen some talk about the radiator fan causing AC issues, but there are no strange fan noises at all- e.g. no excessive noise or overheating or anything. I haven't done a deep dive on this yet. Seems like the issue with the fan + AC interaction is that the fan doesn't run and the AC system overpressurizes and then vents the refrigerant to atmosphere, which doesn't seem very likely (this would also require the AC compressor to be running anyways I think).

 

It's probably just a dead clutch coil if there's no continuity from pin 87 to ground. I replaced mine a couple of months ago.

 

If the fan does not come on then the high side will have high pressure and then the high pressure switch will activate and cut power to the clutch. Does not vent to the atmosphere.