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A/C Compressor won't cycle...

18K views 25 replies 6 participants last post by  kalvinr11 
#1 ·
Just the other night I was cruising down the highway and had the A/C on about 68 and it was working nicely. I stopped for some dinner at a local diner.

Came back to the car and started it up and the windows fogged up hardcore. It was VERY humid out. Hit defrost and noticed that the A/C compressor did not kick on. Thus no defrost.

Ran the diagnostic check through the ACC panel. No faults.

Everything that has turned up in a search has pointed to the over-temp switch on the compressor or the anti-frost switch on the evaporator. The belt moves freely and no unusual noises from the compressor when it was working.

I actually checked the system charge a month ago and it was good. It has always worked well but I have always thought that it put way more drag on my engine then any other car with A/C I have had. Feels like it was shaking the whole car when it was engaged.

Does this diagnosis sound good so far to anyone else that has experienced this problem?

I will have some garage time this evening to actually diagnosis the system. Anything else to look for?
 
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#2 ·
I think theres a way to check if its the switch on the compressor is working or not. Maybe some on else can tell us.

Also I think those compressors use an electromagnetic clutch to engage, so maybe thats worn out as well.

These are just some more ideas.
 
#4 ·
Ok...

Did the troubleshooting that the WIS lists for "Poor or no AC". It basically runs me through testing all relays, fuses and the pressure switch. All of which test fine.

I ended it with testing the lead that goes to the compressor. It shows 14 volts while running. With all these tests completed I can now say that the problem lies with the compressor.

So it's either the thermal shut off switch or the clutch.

It's very tight down there and hard to see. Does anyone know if the thermal switch can be bypassed or if I can run 12 volts directly to the clutch to activate it?
 
#5 ·
I think you should be able to run the compressor from the batt, but don't take my word for it. And if its the clutch, get a new compressor.
 
#6 ·
You should be able to run battery voltage to the clutch to see if it engages. Just don't do it for too long. If the thermal switch is bad, this may make the clutch not engage at all.

I think codesplice is dealing with the thermal switch problem on his car too. I think.
 
#8 ·
Yeah, I'm dealing with the thermal switch issue on mine. After mucking about with it, I *think* I was able to bypass all the magical safeties on the compressor (thermal switch, frost switch thinger, etc). That is, I can get the compressor to engage using full manual control. Still no cold air, so I'm thinking it's a refridgerant issue now. Maybe. Gonna get my buddy at Meineke to recharge my A/C at some point.
 
#7 ·
But is that wire coming off the compressor the only wire I can tap into? If so then I don't think it'll work because I think that wire goes to the thermal cutoff switch before it goes to the clutch... I already have 14 volts at that wire...
 
#11 ·
just swap out the compressor with a used one. i picked one up for my 9-5 used for 100 bucks. it went in yesterday in all of an hour and a half. then half hour to charge it, and it blows cold. i need to evacuate the system again, vacuum it down, and recharge it again...to get it really cold.

but i hear your pain. when i pulled it out, i couldnt even spin the clutch by hand, and the pulley sounded like it was grinding enough to be shakira. it was well worth it for a good used one!
 
#13 ·
Update:
I picked up a used A/C compressor from a recycler off ebay.
Purchased receiver drier, o-rings and PAG oil.

Drained oil from new to me compressor and followed the WIS guidelines on how much oil to add. One of the techs stayed behind to give me a hand. We recovered the refrigerant and threw everything in. No complications at all.

Then we tried to fill it.

We vacuumed it out and filled it with 1.75lbs of r134a. Started the car and turned on the ACC on low recirc. Started to get cold but the pressures started to shoot up really high. High side was about 250 and low side was climbing up around 90 I want to say.

So tonight he is going to recover, vacuum and refil again.

I'm hoping my expansion valve is not messed up...
 
#15 ·
250 sounds a bit high even for the high side. When you shut the car off, did both sides equal out (with gauges still attached and open)? That is important to take note of and can lead to other issues if they don't equalize in a timely manner. I think my TXV may be sticking because I have fresh 134a in it and still have mediocre A/C performance in hot weather.
 
#16 ·
Have you done a system diagnostic? I think you press Auto and Off at the same time. Do that and you'll see if you have any faults, if any number other then 0 shows up, then you have a problem.
 
#17 ·
Don't remember if the low and high side equalized afterwards. I will check tomorrow. I have a feeling I will be doing an expansion valve this weekend.

I did a diagnostic 2 or 3 weeks ago when my A/C first went out and there were no faults. I am kinda afraid to run the system with the pressure that high but maybe I will do another system check tomorrow.
 
#19 ·
I don't think that the diag system in the ACC will give you any faults as to an A/C compressor not cycling. It should only be to tell you about things likes damper doors not opening or electrical faults in dash area that control said dampers.

I wouldn't be too worried about driving with those pressures. As long as your cooling fan is on when the A/C is, your high side pressures should be ok. Plus there should be a high pressure cut off switch that will stop the compressor cycling if it gets ridiculously high.
 
#20 ·
I wouldn't be too worried about driving with those pressures. As long as your cooling fan is on when the A/C is, your high side pressures should be ok. Plus there should be a high pressure cut off switch that will stop the compressor cycling if it gets ridiculously high.
Yeah... As soon as the fan kicks on the high pressure shoots way down... I'd still prefer the system to be more "in spec". Haven't gotten around to futzing with it more.
 
#25 ·
Ok. I think everything is back and working good. Replaced the expansion valve finally. Vacuumed and recharged the system. Low side was reading at about 32 psi and high side around 240 which seems right. Air is ICE cold coming from the vents.

One more question though. The high side still creeps up but the fan kicks on and knocks it back down.

I seem to remember reading something stating that the engine fan should be on all the time as long as the a/c is on? Is that true? Like always on low and then when the pressure creeps up the high speed kicks on?
 
#26 ·
The cooling fan shouldn't be on all the time with the A/C on (last I could remember). It only comes on when commanded on by the PCM as a result of engine over-temp or A/C over pressure. Mine isn't on all the time when the A/C is on. Glad to hear it's working again.
 
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