AC compressor voltage?

**Pontiac99GTP** · 06-01-2011

Ok this is the first time i have had to ever mess with AC. So hopefully somebody can help me with my issue. I get no cold air and the compressor does not turn on. I checked the fuses, diode, and relay that were all associated with the AC..they were all good. I then checked for voltage at the connector for the compressor with the car running....no voltage. I know the system pretty is pretty much empty. My first question is will there be no power at the connector of the compressor if the system is low? I would assume that there should...

**Scottydoggs** · 06-01-2011

when you are out refrigerant the a/c clutch stops kicking in, you have a leak in the system, look for greasy looking areas along all the hoses and pipes and connections in the ac system, those are leaking areas. if you cant find the leak that way you can refill it with leak detector refrigerant.

**whiney** · 06-01-2011

There is a low pressure switch on the suction side somewhere in the car. You need to add the amount it calls for and if it doesn't work start looking at the wiring. Please don't use the dyed leak tester, that stuff is garbage. Look on all of the connections, condenser connections. suction and discharge on the compressor, accumulator, evaporator lines and so on.

**Pontiac99GTP** · 06-02-2011

Ok I just wanted to make sure the reason there is no voltage at the compressor connection is because the system is low before I start chasing in the direction.

So I bought the high/low side gauge set and the refridgerant. I was able to get the low side to 45psi but the high side only went to 50psi. The compressor still wouldn't kick on. Will the high side increase once the compressor decides to turn on and cycle the freon through the system? Or how does that work?

**BillBoost37** · 06-02-2011

At 45psi the low side is higher than it needs to be, and the compressor should have kicked on.

Did you set the AC to on and max cold when you tried this?

**Pontiac99GTP** · 06-02-2011

That's what I was figuring. It said the low side should be between 40-45. Yeah the AC was in full effect. I wonder if I have a bad compressor. The only other thing I am going to look into is the climate control center under the radio. I know it was acting weird after I first put the radio in with all the extra wires I had to jam in there.

**BillBoost37** · 06-02-2011

I'm thinking you can also check the wire at the pcm that gets the AC request from the hvac unit.

**Pontiac99GTP** · 06-02-2011

I tried shorting out the relay for the compressor also. Still no luck. Anybody have any compressor diagnostic tips or tricks?

**PatriotGT** · 06-03-2011

Do you have power on one side of the low pressure switch?

**Pontiac99GTP** · 06-03-2011

There is only one low pressure switch on the high pressure side under the air filter? No I haven't thought to check that yet. I have been able to spend a lot of time troubleshooting it yet.

**SJAndrew** · 06-03-2011

Check to see if you have resistance across the compressor coil.

The compressor's only electricity (power wise - there might also be a lower current pressure switch) is a solenoid based clutch that engages when powered by the relay. If the coil is bad, it will mosty likely be an open circuit at the compressor itself.

I imagine there is little more than a two-pole weatherpack connector @ the coil. Take off the plug and see what resistance you have across the terminals (compressor side not wire side). If it's infinite, you've found your problem: the coil has failed and needs to be replaced. From what I understand, it's relatively simple to fix.

**donkason** · 06-04-2011

I'm having the exact same problem. I was running my AC earlier today and I jumped in a few hours later and nothing. My compressor will not engage. It has been getting warmer over time so I decided to start by putting some refrigerant in the system after reading if it was low the compressor wouldn't kick on. Here is the problem, per the instructions on the can of refrigerant the compressor has to be running to put refrigerant it. I tried without it running and it pinned the pressure gauge and nothing would go in.

Is there a way to get this stuff in the system without the compressor running?

**SJAndrew** · 06-05-2011

I charged mine when the level was too low for the compressor to spin.

It took a couple of bottles of freon to get it fully charged. It's been fine since (~2 months ago - still ice cold).

**Pontiac99GTP** · 06-07-2011

My situation turned out to be a bent pin on the compressor connector. Was able to straightn it out after messing with it forever and were in good shape now. Going to charge it this afternoon. Thanks for everyones help.

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