A/C: Compressor won't kick on
Thread Starter
Drifting
Joined: Feb 2015
Posts: 1,440
Likes: 1,031
From: Baton Rouge Louisiana
A/C: Compressor won't kick on
My AC was working fine and blowing ice cold until I went to drive my vette last week and the compressor wasn't kicking on and it is blowing hot now. The AC light blinks for a few seconds then turns off and the compressor never kicks on. I put a manifold on it and it read 48PSI on the low side and 90PSI on the high side, but this is with the compressor not kicking on. I switched the horn relay with the AC clutch relay and still no luck.. Is my compressor bad? I also checked the for HVAC codes and there are none present in my DIC. It wouldn't take a charge either, not sure if it needs any freon though.. Anyone have any insight on this? What else should I try to further diagnose?
Last edited by Arg0413; Jun 7, 2015 at 03:56 PM.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Something is very wrong is you have a differential pressure between the high and low side with the system NOT RUNNING! 
The pressures SHOULD be equal! With the engine OFF and COLD, read the high and low pressures again.
IF,, the system pressure is below the low spec, the compressor will not come on.
HAve someone turn on the AC while you observe the compressor INNER HUB. See if it spins and then quits (indicating that it saw too low of suction pressure and then shut down)
BC
The pressures SHOULD be equal! With the engine OFF and COLD, read the high and low pressures again.
IF,, the system pressure is below the low spec, the compressor will not come on.
HAve someone turn on the AC while you observe the compressor INNER HUB. See if it spins and then quits (indicating that it saw too low of suction pressure and then shut down)
BC
Thread Starter
Drifting
Joined: Feb 2015
Posts: 1,440
Likes: 1,031
From: Baton Rouge Louisiana
Something is very wrong is you have a differential pressure between the high and low side with the system NOT RUNNING!
The pressures SHOULD be equal! With the engine OFF and COLD, read the high and low pressures again.
IF,, the system pressure is below the low spec, the compressor will not come on.
HAve someone turn on the AC while you observe the compressor INNER HUB. See if it spins and then quits (indicating that it saw too low of suction pressure and then shut down)
BC
The pressures SHOULD be equal! With the engine OFF and COLD, read the high and low pressures again.
IF,, the system pressure is below the low spec, the compressor will not come on.
HAve someone turn on the AC while you observe the compressor INNER HUB. See if it spins and then quits (indicating that it saw too low of suction pressure and then shut down)
BC
Also, My AC clutch doesn't to anything when I have someone press the AC button and I watch it.. It just sits still the whole time.. (pulley is turning of course)
Last edited by Arg0413; Jun 8, 2015 at 01:41 PM.
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Thread Starter
Drifting
Joined: Feb 2015
Posts: 1,440
Likes: 1,031
From: Baton Rouge Louisiana
Drifting
Joined: Feb 2008
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From: Bahama North Carolina
Here is a link to help. https://www.corvetteforum.com/forums...re-sensor.html
Thread Starter
Drifting
Joined: Feb 2015
Posts: 1,440
Likes: 1,031
From: Baton Rouge Louisiana
I ordered an ambient air temp sensor yesterday, changing it as soon as it comes it. Hopefully that'll get her working again. However, I don't understand why I have a static pressure differential between the low and high side.
Instructor
Joined: Jun 2014
Posts: 189
Likes: 20
Something is very wrong is you have a differential pressure between the high and low side with the system NOT RUNNING!
The pressures SHOULD be equal! With the engine OFF and COLD, read the high and low pressures again.
IF,, the system pressure is below the low spec, the compressor will not come on.
HAve someone turn on the AC while you observe the compressor INNER HUB. See if it spins and then quits (indicating that it saw too low of suction pressure and then shut down)
BC
The pressures SHOULD be equal! With the engine OFF and COLD, read the high and low pressures again.
IF,, the system pressure is below the low spec, the compressor will not come on.
HAve someone turn on the AC while you observe the compressor INNER HUB. See if it spins and then quits (indicating that it saw too low of suction pressure and then shut down)
BC
The pressures should be about equal with the system off. Your static pressure should be about the same as the ambient temp. Something you can try to see if the compressor is working is jump the terminals on the low pressure switch even it the pressures are to low to turn the compressor on jumping the low pressure switch should click the compressor on.
Thread Starter
Drifting
Joined: Feb 2015
Posts: 1,440
Likes: 1,031
From: Baton Rouge Louisiana
The pressures should be about equal with the system off. Your static pressure should be about the same as the ambient temp. Something you can try to see if the compressor is working is jump the terminals on the low pressure switch even it the pressures are to low to turn the compressor on jumping the low pressure switch should click the compressor on.
Tech Contributor
Joined: Dec 1999
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
The Pressure Transducer is a solid state device and NOT a switch so,,,,,, you just CANT jump it. I would be afraid of damaging the circuit/PCM
That said, look at the high prssure line just forward of the coolant tank. You will see the sensor.
BC
That said, look at the high prssure line just forward of the coolant tank. You will see the sensor.
BC
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
One way the system equalizes its self is through the orface tube. If its clogged, it could contribute to th pressure differential. When the HVAC is first turned on, do the gages do anything?
Bill
Bill
Thread Starter
Drifting
Joined: Feb 2015
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From: Baton Rouge Louisiana
The HVAC won't turn on, but when I start the car or attempt to turn the AC on, the gauges don't budge.
Thread Starter
Drifting
Joined: Feb 2015
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From: Baton Rouge Louisiana
UPDATE: Replaced the ambient air temp sensor today and my HVAC control panel now reads the correct temperature. However, my A/C still blows hot and my compressor still won't kick on. Is my next step to drain my system and inspect the orifice tube?
Thread Starter
Drifting
Joined: Feb 2015
Posts: 1,440
Likes: 1,031
From: Baton Rouge Louisiana
Update:
I did some more trouble shooting of my AC system and I still haven't solved the problem.. I pulled the relay and tested the circuit, it's getting power! I jumped it and the AC compressor kicked right on and I got a proper pressure reading, it was perfectly fine... The relay isn't going to ground and this must be what is preventing the compressor from kicking on. So what would cause this? Does the PCM ground the circuit to kick the compressor on? Is there a ground somewhere I need to check?
I left the circuit jumped and removed the relay for now so I will have a working AC.
I left the circuit jumped and removed the relay for now so I will have a working AC.
Thread Starter
Drifting
Joined: Feb 2015
Posts: 1,440
Likes: 1,031
From: Baton Rouge Louisiana