You've got a good thermostat, a good heater core,coolant is flowing, and yet.....NO HEAT! What gives?

Todauy we'ree looking at the Heater Control Unit (HCU)- the commander that tells the heating system what you want it to do. And sometimes, that command has to travel to a component you may know as the hot water valve, but the manufacturer may call something completely different.

Case in point: a Crown Victoria that had visited multiple shops on the Hamilton Mountain without anyone finding the reason it wouldn't make heat. The wiring diagram finally revealed the culprit hiding behind a very fancy name: thermal blower lockout.

Yep. That was the hot water valve.

Before winter catches you off guard, you want to know that the HCU can actually command that valve ...