Cab heater issues

Check under the hood. There's usually a valve in the lines from radiator to heater core. Might be on the supply side to the core, might be on the return, or both.

 

Look for these under the hood on passenger side of engine.

 

The valves to the cab were probably shut off during the replacement of the cab heater core, and never turned back on.

 

Mixer valve might not have been plugged back in/connected. That's the valve connected to the temp dial inside the cab. It's run by a servo motor these days. Usually if the water is shut off you won't have heat in the bunk, either.

 

If you have a battery switch turn it off or take the ground off your battery for a little bit. Could just be a computer issue for the climate control. My 2017 579 would do that once in a while, or a couple times the a/c wouldn’t get very cold but it would go back to normal after I unhooked the batteries for a few minutes.

 

Seems to be a common problem on the 579s.