I’m working on a 2017 PB348 with a PX9 Paccar engine. The AC has been intermittently failing. Today I just happened to get the truck while the failure was occurring. No Ac, charge was good, had power to both pressure switches, no power to compressor coil. I checked the fuses and swapped the relay. I swapped the HVAC control panel with a known good one from another truck (PN Q21-6119) and the ac was working great. The driver took the truck to the job. When the driver returned he informed me that by the time he got to the job the AC had quit working. He left the truck off for approximately two hours and on the return trip (about 40 minutes) the AC quit working at about the halfway point. I did all of the same checks as this morning, fuses are good and I have power at both switches. Charge is good. I reinstalled the AC control panel that I removed this morning and everything works good.
Is there something that could be causing this AC control to get hot or short out?
PB ac problems
Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Doberman83, Jul 29, 2025 at 3:24 PM.