2008 Prostar a/c clutch won't engage, no fault codes.

2010 is a change over year. Not sure if it depends on which engine. Anyways, when the pressure circuit goes open or high resistance the body controller with lower software revisions will see that as high pressure. So you might have wiring problems. 95% of the time, the connector and first 3 inches of wiring from that connector at the sensor is the problem.

 

My 2010 has them

 

Has what?

 

Heavyd
I have a 2010 ProStar with a ISX and the a/c clutch stays engaged all the time, this includes with the key off. Can you help??

 

Disconnect the electrical connector and see if the clutch disengages. If it does disengage, then it is being powered by a 12 volts constantly and will need further troubleshooting. If you disconnect it and it still stays engaged, then the clutch is seized and you need a new compressor.

 

I have done that and it is not the clutch. Were does the power come from to the clutch. Is it the cab controller or is there a relay in these things? I changed the control head in the dash so it is not there.

 

That is a direct output from the body controller.

 

This is a rare fix, but any time the body controller starts to do weird stuff, it is best to perform a cold boot. Only way to do this is disconnect the batteries for 30 seconds.