2006 Tahoe/AC charged but Compressor not turning

[glmoore0001]

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]

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.

 

[OR VietVet]

Does it work if you unplug the low pressure switch at the accumulator and cross the connection?

 

[Miami-Dade]

Moved you here from 2021+section

 

[UmmScott]

So...
Is the belt still on?
There is a separate belt and tensioner solely for the ac compressor

 

[nonickatall]

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

 

[glmoore0001]

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.

 

[glmoore0001]

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.

 

[glmoore0001]

So...
Is the belt still on?
There is a separate belt and tensioner solely for the ac compressor

Yes the belt is on and the outer pulley on the compressor is turning.

 

[glmoore0001]

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.

 

[UmmScott]

Yes the belt is on and the outer pulley on the compressor is turning.

If the outer pulley is also turning, then your clutch is engaged

 

[glmoore0001]

Moved you here from 2021+section

I'm sorry about that. For some reason when I made the post, I couldn't see but one category.

 

[glmoore0001]

If the outer pulley is also turning, then your clutch is engaged

I figured that if the nut in the center of the compressor was not turning that the clutch was not engaged. Isn't the center hub of the compressor what turns the compresses ?

 

[OR VietVet]

The "outer pulley" is what the belt rides on and that spins at all times when engine is running. The outer part is the clutch and has no pulley and only spins if is engaged.

@glmoore0001, when you unplug the switch at the accumulator and cross the wires/harness, with a jumper wire, all you are doing is checking to see if clutch will engage when given a signal to do so. You would be bypassing the switch at the accumulator. The switch itself may be bad if the clutch engages and the a/c blows cold. You are not low on refrigerant because of the static pressures you posted. On your a/c and heater control in your dash, do you have a top right button that says "AUTO" on it. That would mean you have an auto temp control but you can operate it all manually, exactly like I do, when you turn on your a/c by pressing the "snowflake/* " button. If a/c works on one and not the other, you have a control head problem or a problem with sensors that give info to the control head. If it works on either one of them, when you jump that harness of the switch at the accumulator, you have a bad switch. There is also a high pressure switch at the back of the a/c compressor. If you do have gauges and the a/c does function when you jump the harness at the accumulator switch, post those pressures.

 

[UmmScott]

Right..
Sorry if I cause confusion with the outer pulley terminology.

The clutch is on the outside/front of the belt pulley on the compressor

 

[nonickatall]

So if I check continuity on a bad pressure switch it will be open?
Thanks for the info.

I dont now what is the situation with a bad pressure switch.
But in a working system, the pressure switch is switched to continuity, when there is enough pressure.

 

[glmoore0001]

I dont now what is the situation with a bad pressure switch.
But in a working system, the pressure switch is switched to continuity, when there is enough pressure.

Thank you. That is the info I was looking for.

 

[glmoore0001]

The "outer pulley" is what the belt rides on and that spins at all times when engine is running. The outer part is the clutch and has no pulley and only spins if is engaged.

@glmoore0001, when you unplug the switch at the accumulator and cross the wires/harness, with a jumper wire, all you are doing is checking to see if clutch will engage when given a signal to do so. You would be bypassing the switch at the accumulator. The switch itself may be bad if the clutch engages and the a/c blows cold. You are not low on refrigerant because of the static pressures you posted. On your a/c and heater control in your dash, do you have a top right button that says "AUTO" on it. That would mean you have an auto temp control but you can operate it all manually, exactly like I do, when you turn on your a/c by pressing the "snowflake/* " button. If a/c works on one and not the other, you have a control head problem or a problem with sensors that give info to the control head. If it works on either one of them, when you jump that harness of the switch at the accumulator, you have a bad switch. There is also a high pressure switch at the back of the a/c compressor. If you do have gauges and the a/c does function when you jump the harness at the accumulator switch, post those pressures.

Thank you for that information!
I have to drive from Rockford, IL. To Winnipeg Manitoba this weekend. I am not sure when I will post again on this subject. Gary

 

[Mudsport96]

Are you gettig 12v to the compressor plug? That is where you should start. If yes then the coil could be bad. Or the clutch is too worn and the coil cant pull it in because the air gap is too big.
So first find out if you have power at the plug.

 

[glmoore0001]

Ok. Power to the clutch is possible.
But as explained, the problem began as a properly working ac.
Then turning off the snowflake button did not stop the cooling.
Then when it did turn off, it would not turn back on. Period.
I first though of controls,swapped relays with the horn and no change. Then checked system pressures., all good.
I hopefully will get to it today to try some tests.