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

Is it getting power to the plug?

 

And a good ground back from the plug?

 

i just had the same thing on a classic. brand new clutchs but would not engaged. took new clutch off other truck that worked for testing and it worked on broken truck. new parts failure. after doing some homework found that if parts where mailed and scaned at some point it can de magnize the coil pack for good.....another new clutch and works great.

 

The A/C on a Prostar is all computer controlled. Power to the clutch is sent from the body controller. The body controller is monitoring for inputs from the driver controls, temperature thermistors and a/c high pressure switch. To power the clutch the body controller must see an input from the driver controls, thermistors must be 28 degree F or higher. Body controller must see some pressure in the system, (not sure how much) to allow the compressor to run. There really isn't anything you can do if you cannot monitor the body controller with Diamond Logic software. If this guy just had all this work done, why is he coming to you? If the work wasn't done right he should be taking it back.

 

Yah, I hear that! Glad to hear it is working good now. The thermistors are used so the body controller can monitor how cold the system is to prevent it from freezing up. When a thermistor is bad, usually open, that translates to a reading of zero degrees F. Since zero degrees is less than 28 degrees, the computer thinks the system is cold enough and will not run.

 

Where are the thermistors located

 

Right side firewall area tapped into the ac lines that go into and out of the evaporator. There are no thermistors in 2010 and up Prostar trucks.

 

I have a 2011 Prostar built June 2010 with the Cummins ISX 400 and I have thermistors. I'm assuming you are referring to 2010 and up MaxxForce equipped ?

My problem is excess high pressure shutdown until key cycle . Thermistors and high pressure switch have been replaced . I've been told by dealer mechanics replacing the thermistor connectors and sealing them is a waste of time .

The thermistors are new so I'm doing the rest as recommended by International and replacing the high pressure switch which is less than a year old .

I'll update next week ...

Frank