A/C Compressor does not turn on

Tiny
VINTSHAVE
  • MEMBER
  • 1993 CHEVROLET CAPRICE
I recently noticed that my car A/C was not blowing cold AT ALL. I checked under the hood and noticed that I didn't even get a "click" when someone turned the A/C on. Like a dweeb, I went out and paid $28 bucks for a replacement A/C Cutoff Switch (the round thing that gets seated in the oil in the compressor). I didn't first check the power to the switch like I should have (doh!). There is no power going through the wires to the switch and just a few microvolts of change on the meter when I turn the A/C on and off. So, no power to the compressor = no A/C. The problem is, I can't figure out where the damn wires go and there is no obvious fuse or relay that controls the power to the compressor.

I'd appreciate it if you could tell me:

How much power should be going to the compressor?
Where the power source is for the two wires (I think one is dark blue and the other light blue)?
What fuse/relay controls the power to that switch?
What are the next steps in repairing this issue?

I checked every fuse in the fusebox in the side of the dash and they are all good.

HELP!

John
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Wednesday, May 1st, 2013 AT 1:56 AM

7 Replies

Tiny
MHPAUTOS
  • EXPERT
The first thing that you need to do is see what pressures are in the system, if you have a leak and the system is low on refrigerant, there are safety systems in place to stop the clutch coming on as low refregrant can cause damage to the compressor, so check system pressures first and ensure that you have the correct weight of refrigerant in the system to start with.
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Wednesday, May 1st, 2013 AT 2:04 AM
Tiny
VINTSHAVE
  • MEMBER
How would I do that? Would I just use a regular pressure gauge? What is the expected pressure for the system on this car?

If I have no/low refrigerant, can I used another refrigerant other than R12? I would hate to have to bring the car in just to get a refrigerant charge. But if I have to, what is a fair price to charge the system with R12?
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Wednesday, May 1st, 2013 AT 2:33 AM
Tiny
VINTSHAVE
  • MEMBER
Follow up question. What makes the wiring that goes to the compressor aware that the refrigerant pressure is low?
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Wednesday, May 1st, 2013 AT 3:04 AM
Tiny
VINTSHAVE
  • MEMBER
2nd follow-up question. Sorry

Is there a sight glass where I can see how much refrigerant is in the system? If so, where can I find it?
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Wednesday, May 1st, 2013 AT 3:56 AM
Tiny
MHPAUTOS
  • EXPERT
You need a duel pressure gauge to check system pressures, if the pressure is down there is a low pressure switch in the system that will shut down power to the compressor, guessing refrigerant levels is no good, they are set at a precise weight and if over or under the system will shut down or be very inefficient, this should be referred to a A/c tech to be checked correctly.
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Wednesday, May 1st, 2013 AT 2:16 PM
Tiny
VINTSHAVE
  • MEMBER
I found out that the screw fitting on the lower (cold) steel line running from the condenser and then to the firewall is leaking. I have tried to screw it closed and replaced the O rings, but it just doesn't feel like it is threading down all the way and compressing the O rings. I'm afraid of going any tighter because I think it will break the line. It could be thread damage. What could I do short of replacing the entire line and possibly the condenser to fix it?

Also, does putting the system under vacuum for 20 minutes suck out all the Ester oil? Do I need to add more?
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Tuesday, May 14th, 2013 AT 8:25 PM
Tiny
MHPAUTOS
  • EXPERT
You will need to add some more oil, best to check leaks with comp air charge and vacuum as seals can leak under pressure or vacuum.
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Saturday, May 18th, 2013 AT 3:15 PM

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