2006 Tahoe/AC charged but Compressor not turning

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glmoore0001

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I ran the AC in my 2006 Tahoe Z71 4wd yesterday to cool down the car, when I turned the system off the AC still blew cold air.
I turned the AC button on and off a few times and it finally made a long fading squeak and the the cooling shut off.
The AC icon shows on the HVAC panel when the button is pushed but the compressor will not kick on.
I swapped the AC relay with the horn relay and it did not change.
The AC 10 Amp fuse is not blown.
I put gauges on the system with the engine off and I show 125 psi on the high side and 115 on the low side.
Did I have some type of valve failure in the system?
Maybe a failure in the dash controls?
Thanks... Gary
 

OR VietVet

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I would say dash controls. Will it work on either auto or manual selection? The pressures are close to equal and that IMO is just fine. They should be equalized when compressor is not engaged.
 

nonickatall

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There is not valve. There is a pressure switch which check if the correct pressure in the system is available and a magnetic clutch, which will be engaged from the control.

Check if it makes a sound on the compressor, when someone in the car engages the ac.

If not. Check, if the pressure switch on the charcoal dryer is open.
If not. Put a wire in the connector, to shortcut the switch.
If your compressor not start, put 12v on the magnetic clutch, which is the conector direct on the compressor.

Most reasons for not running ac are in order of appearance:
Low cooling gas
Pressure switch defect
Failed magnetic clutch
Failed magnetic clutch Relais
Failed compressor
Failed control
 
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glmoore0001

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I would say dash controls. Will it work on either auto or manual selection? The pressures are close to equal and that IMO is just fine. They should be equalized when compressor is not engaged.
If it can be auto engaged, I have no idea. I have always used it in manal mode.
 
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glmoore0001

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Does it work if you unplug the low pressure switch at the accumulator and cross the connection?
I was not sure if it was ok to do that, but I thought of it. The accumulator is on the passenger side of the dash correct?
I pulled the connector while the truck was running and nothing changed. There was also a switch located near the compressor, I did not mess with that one.
 
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glmoore0001

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There is not valve. There is a pressure switch which check if the correct pressure in the system is available and a magnetic clutch, which will be engaged from the control.

Check if it makes a sound on the compressor, when someone in the car engages the ac.

If not. Check, if the pressure switch on the charcoal dryer is open.
If not. Put a wire in the connector, to shortcut the switch.
If your compressor not start, put 12v on the magnetic clutch, which is the conector direct on the compressor.

Most reasons for not running ac are in order of appearance:
Low cooling gas
Pressure switch defect
Failed magnetic clutch
Failed magnetic clutch Relais
Failed compressor
Failed controls
So if I check continuity on a bad pressure switch it will be open?
Thanks for the info.
 

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