A/C Always On?

[taenumbanine]

My AC compressor doesn't shut off unless I pull the under hood fuse. Does anyone have any suggestions on what needs a replacement?

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[03z71chevy]

Are your rear HVAC controls on at all? I seem to remember that if I have the rear HVAC set to anything the compressor runs. Also if I have my front HVAC set to AUTO it will run the compressor non stop so I almost always have that setting off.

 

[taenumbanine]

No the hvac isnt set but I could plug the fuse in now and as soon as the pins make contact the compressor will start up.

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[03z71chevy]

So the compressor runs with the front and rear HVAC off?

 

[taenumbanine]

Yeah and it drained my battery once or twice before I wised up

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[03z71chevy]

That's odd. Hopefully someone on here has an idea.

 

[mizzouguy]

Am i missing something? The compressor wont turn unless the engine is running. And the clutch wont get power to engage the compressor unless a whole bunch of parameters in the ac system have been met (low pressure switch, high pressure switch, etc). I'd have to look at a wiring diagram but if I remember right, the control unit in the dash is what receives signals from all of the sensors and then gives power to the clutch.

 

[taenumbanine]

So are you saying my control unit is bad?

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[mizzouguy]

Help me fill in some blanks. Truck is not running, key off, and compressor clutch is energized while not spinning? As in it has 12 volts at the clutch connector? Start the truck and the compressor is always engaged no matter what you do with the controls inside and the clutch only disengages when you pull the fuse, effectively cutting the power source?

 

[taenumbanine]

Yes, key off, the compressor is being fully powered up until I pull the fuse.

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