The ac compressor will not engage intermittently. Occasionally it will come on and works perfectly. I recently replaced the compressor, well everything except the rear evaporator. That leaves the ecm and harness. Originally the compressor stopped making pressure and hence the replacement. I need to know about the high pressure switch control of the ecm. Control unit in dash was replaced. What should the voltages be on those three wires and any other thing that would tell the ecm to shut down.

Brian

 

How about the condenser cooling fan? If the fan is not working, it will not condense the refrigerant back to a liquid. Pressure will be too high and the clutch will not engage.

Check for a seized fan, blown fuse, wiring issue or fan motor issue.

 

I'll look at that. I'll post when I check.
Brian

 

Back to work on uplander and everthing works as it should. I only drove 10 miles though. Fans cycle as they should. If it overheats it should show warning message on the display. When it does go out I have no ground at the relay from the ecm. I reckon I will get another new hi pressure switch. It can sit for a day and work or not hot or cold. Weird. Going to do a longer ride and let it stop working and check voltages again.

 

A/C is still working now in September.

 

Who did the work on your system? If you, did you vaccum the system down to -30 PSI for at least 1/2 hour? If you have atmo in the system you wont stop this issue at all and it would ex[lain why your pressures are too high as well.

 

Glad to hear it! Carry on!