Freightliner FLD,very hot in cab

As the weather gets colder, I opened up the valves to supply hot coolant to the cab heater to warm up the cab in the morning.

The problem is that it is very HOT even when heat is turned off. So I have to stop the truck and just close those valves. I wish I could just turn off heat from the cab control.

Does anyone know if this is normal or not?

2000 Freightliner FLD.

 

Guys, thanks a lot. Where are those valves, where can I find them on the truck?

 

you mean in front of the transmission shifter? On my truck there is a fuse box there... But I figure that it is probably somewhere in the front part of the cab?

 

A little followup: I adjusted the cable from the hot/cold control lever that was going to the hot water valve. It seems to work better and makes almost no heat when I turn heat off (unlike before when heat was unstoppable). When I turn heat on, it makes heat. Even down to negative temps I seem to be okay.