1997 850R AC will not turn on

phatjacques · Post by **phatjacques** » 10 Sep 2014, 10:10

Hello I am new to MVS but have been reading a lot of the posts and found it to be extremely helpful. Recently I just changed out my AC compressor (I shimmed it before I put it in!) and changed out the receiver/drier and orifice tube as well as O-rings, charged my system with no leaks! The bad news is the AC will not turn on. I ran a hot wire to the compressor to check to see if the clutch moved/engaged and it did. I am stuck and need a bit of help. My mechanic thinks it could be the high side pressure switch, but after reading I tend to think it could be the AC relay (glove box) or the AC thermal cutoff on the compressor itself. Any thoughts on how to diagnose or fix these?

phatjacques

Post by **rspi** » 10 Sep 2014, 10:36

Have you checked the high and low pressure switches to see if they are open or closed?

phatjacques · Post by **phatjacques** » 10 Sep 2014, 11:06

I actually have not, but I did think about that as well. I am not sure how to do that though. I will look on the VRD. Any other ideas?

phatjacques

Post by **jblackburn** » 10 Sep 2014, 12:48

The low-pressure switch is on the AC line entering the firewall at the top, passenger side of the engine compartment. Remove the plug and jumper the contacts with a piece of wire and see if the compressor kicks in.

The high-pressure switch looks similar, and is slightly below the plastic air intake tube for the computer box towards the front of the car.

phatjacques · Post by **phatjacques** » 10 Sep 2014, 13:58

I tried to jump it but the compressor would not turn on. Does this mean that the low pressure switch is bad or that it isn't getting power? Thanks.

phatjacques

'72 240
'92 740 turbo wagon
'97 850 T5 wagon
'97 850 R

Post by **phils94850** » 10 Sep 2014, 15:07

phat.. i went thru this on my 850r.. it ended up being some melted wires going to the a/c relay behind the glove box. When you turn the a/c on you should hear it "click" if its not, then i would start there. Also.. how much freon did you put in it ? I think mine used about 2 cans if i remember correctly, you know it wont come on if its overcharged or undercharged so you have to get it right.

phatjacques · Post by **phatjacques** » 10 Sep 2014, 15:28

phils94850 thanks for your reply. I haven't checked the relay yet. I am going to take it out today and test it. I think I ended up putting like 24 lbs into the system (2 cans) so it is just under full. I think it is supposed to have 26 lbs. Did you check the relay yourself or just knew it was bad b/c of the wires?
PJ

Post by **abscate** » 10 Sep 2014, 15:47

phatjacques wrote:phils94850 thanks for your reply. I haven't checked the relay yet. I am going to take it out today and test it. I think I ended up putting like 24 lbs into the system (2 cans) so it is just under full. I think it is supposed to have 26 lbs. Did you check the relay yourself or just knew it was bad b/c of the wires?
PJ

Just noting for future readers that CA pounds are what most people call ounces.

Both relay and wiring need to be evaluated. Before you do this, see if you get 12VDC onto the low pressure switch when you turn on the AC. Then trace back that circuit to the relay.

You could have a break in the low pressure switch to compressor circuit, rule that out first.

phatjacques · Post by **phatjacques** » 11 Sep 2014, 07:59

Thanks Abscate, yes it is 26 ounces, not pounds, lol. The low pressure switch has power to it
phat

Post by **abscate** » 11 Sep 2014, 11:14

Low pressure switch has power, but the compressor doesn't pull in when jumped?

That's pointing to a bad low pressure switch to compressor wire. How did you apply 12 VDC to the compressor to successfully make it pull in? If it was by disconnecting the compressor plug you have the dragon by the tail