I was driving in the rain the other day and had to add a little heat to my defogger to keep the windows clear. Since then it seems the heater control is all the way open no matter what position the **** is in. Anyone have any ideas if this would be electrical in the switch or mechanical at the heater core. I had this happen once before where it would not get warm. After shutting the car off for a few minutes the system went back to normal. Need to figure this out as I am baking in the car because of the flow through the heater core and the positive ventilation system blows the heat into the car. I am in Florida where it is 90 degrees + daily. Any help would be appreciated.

 

There is a blend door actuator that controls the heat. It is located under the dash on the top of the heater box. It is highly possible that is your problem. If it is not in the switch. The switches are known to break the back side off and just spin on the control.