I am helping my mom with her truck while I am in town. She is not getting any hot air in the cabin even though the temp gauge reads normal operating temp and the heater control unit is turned all the way to hot. Could this be a termostat or is there something with the heater control unit? I dont think it is a thermostat because it heats up just fine but it is like it is not heating up all the way like a thermostat opening to early. Any help is apreciated.
did you manually check the control valve to see if it is working. IE when some one turns the control to cool then back to hot is the arm moving or isit rusted shut? run into the problem many times. if not then I agree with Tcmaboy it is the core.