Issue with HVAC system - Random shut off

Hello. I searched the forum and could not find a related post. Maybe I didn't search properly. Long time lurker on the forum for other topics.

I have a 2012 Freightliner Cascadia (Cummins ISX) with two issues. Going to talk about the one that is more serious to me. The HVAC system will randomly cut out and won't work until I shut the truck off and turn it back on then it will repeat at random times. Sometimes I can drive for hours without it shutting off and sometimes only 5 minutes. Running the truck idle it would do the same thing. Either run for a long period or shut off.

It seems to be doing this with AC on or off. The sleeper controls work for a certain time after the front shuts off but then it too will cut off (checked this one time). There was a dash code but forgot to write it down when it happened. I moved to the east coast from the west and it worked just fine through the trip. Let the truck sit for two months. Issues started happening after we had trouble starting the truck and battery had some loose connections on the terminal. Became an O/P start of the year and bought the truck same time.

Replaced the blower fan and the control module on the dash but same issue persists. Fuses are fine. Maybe someone has some knowledge were to look next or troubleshoot. Wondering if maybe someone has diagrams of the system. I am not a mechanic but I try and do what I can.

Thank you.

 

Thanks for the reply. I forgot to put in the post that I have done that. Multiple times. I even cut the batteries in the truck and then started it up, and tried it.

I am going to trace the wires and see if maybe I have a bad connection somewhere in the dash.

 

I have checked the fuses on the firewall drivers side, ones in the box in front of the firewall and in the passenger dashboard (SAM Chassis?). I tried to see what I can find related to HVAC. Did not find any bad fuses. Just in case I saw a fuse that looked off I just replaced it. There were some fuses missing in different areas that I checked but I am guessing they are not there because the truck doesn't have that function or not needed.

Today I checked the wires where they are leading to (that I can get to without taking the dash fully apart). Found couple fuses inline on some wires center dash. All looked good. We did check the starter and found a wire that seems to have broken off. We redid it and will see if that caused the issue to the HVAC system.