I have a 2001 Freightliner Century and I replaced the heat switch, but now it only blows hot air and when you turn it down it still blows hot air, Im not sure what it is does anybody have an idea of what it might be.
look behind the air filter assembly in the engine compartment.you will see your heater control valve.it will either be cable controlled or it will be electronic.see if when you adjust the temp on the dash that the valve cuts the flow of coolant.there are other possibilities,so keep us updated.good luck.