2017 Peterbilt 579 Heat not properly working

Are you using a foam cleaner?

 

Have you verified the actuator and blend door are fully cycling to their stops, when using your heater controls? This is something one our techs mentioned with my truck.

 

I’m not sure. That’s getting beyond my knowledge.

I only know what I do, because I’ve had a few problems with mine. The whole dash has to come out to completely fix the thing. Seems ridiculous, to design stuff like this.

 

Always hot, when I need it.

I have outside air, somehow, blowing through the box and out the left end of the dash. Depending which way the wind hits the truck, changes how much air comes out the vent. Some days, my left arm and leg are frozen.

 

Weird that usually fixes it. My guess is the actuators may be gummed up. Also do you have that annoying issue with condensation building up on the front window overnight? Not just a bit but almost fully covered?

May have some water in the system someplace if so. And if so it may be a shorting out issue that a dealer needs to eyeball. At this point though if everything is still not working it may be time to stick a snake cam (borescope) down a vent and verify the doors are moving. If they arent try spraying some compressed air down in there several times to see if they loosen up as dirt may have accumulated. If they move then take it to a detailer. The one i use has a special tool they stuff down the vent that does a good job of cleaning it.

If it does move freely right off it may be an issue somewhere else in the system, could even be the controls. The ones in my rig stopped working about 2 weeks after i got my truck and had to be replaced. If you have light out on the control switchs that could be an indicator of issues. Otherwise im stumped.