Heater blows cold air on 1992 GMC Yukon

Is there a heater water control valve and how do I replace/check it? Where is it?

Asked by for the 1992 GMC Yukon
First of all, make sure the coolant level is OK, and the engine is reaching normal operating temperature.

Your vehicle has a temperature blend door, and it is activated by a little electric motor called an actuator. Check out for instructions!