i work in a "small" family owned shop. we have 12 trucks all pete's, from day cabs to straight trucks to sleeper unit trucks. as old as 2005 and new as 2019.
Every one of our trucks have the exact same A/C control unit in the dash (standard plastic, black, nothing special).
On almost every single on of these units we end up having the common failure of the fan switch plug getting burnt up, either on the module side or the pigtail going into it from behind the dash, or both.
We've replaced multiple of these units for about $400 a pop, and now have found just the replacement fan switch online (the problem).
MY QUESTION IS: Is there some sort of TSB on this issue? what is causing this on every single one of our units? Is there something I (as the mechanic) can do to prevent these failures? other than replacing units every year or so ?
for example: our 2019 truck has a "breaker fuse" that controls the fan unit, it would get hot, pop the breaker, and then cool down and work again only to pop again down the road.
sometimes it melts the connection, others just have visual brown spot heat signatures.
i know that it is a common problem with these control units, but what can i do to prevent this from continuing to plague our fleet?
Peterbilt faulty fan switch on dash
The older trucks do have issues with melting blower speed switches. If you find a melted switch/connection you need to check the current draw of the blower motor. Increased amp draw will cause excess heat and melt the weakest connection in the circuit.
Newer 579 chassis do not have issues with fan switches or controllers. If the blower is cutting off it is likley due to other faults in the HVAC system causing the blower to cut off.
Specific models have thier own problem areas and some parts have been updated depending on the specific truck model and year.
i stand corrected, our newest truck is a 2018 389.
this truck seems to be haunted sometimes, multiple times driver has reported dash lights not working, radio not working, OAT not working, all intermittent and randomly. the truck has 10k miles approximately. multiple times me and the other mechanic have walked past the truck at night and the radio would be on with no key in it. very strange lol.
Thank you for the reply. I will keep that in mind the next time we come across this issue.