Hello,

My two cents worth...............

Turn the temp dial to hottest setting.
If its blowing cold air only, check the heater valve [on/off] and the aux water pump.

The aux pump can fry your climate control unit if its been sticking etc, draws to much current. Bad design really considering this runs most of the time.

They should have installed an aux relay to control the aux pump and the heat valve.

You can feel if hot water is going through both of these.

good luck

Brian