1997 Ford F-150

Heater problem
1997 Ford F150 V8 Two Wheel Drive Automatic 112, 00 miles

I have no control of the heating/cooling temperature on my 1997 f-150 with 112, 00 miles. Both the air conditioner and heater work fine, but it appears that the blend door changes position randomly. When the system is operating I can hear what I believe is the blend door popping open or closed, followed by a change from cold to hot air or vise versa.
Joe Boyle
August 10, 2009.

Temperature control knob controls a blend door potentiometer which controls an electronic temperature blend door motor. Temperature blend door motor provides a variable number of temperature blend door positions. When temperature control knob is in COOL position, temperature blend door shuts off airflow to heater core. When knob is in WARM position, air is directed through heater core. When knob is in intermediate positions, heated air is blended with cooler incoming air to achieve desired temperature.
Can be this is defective, and switching the demand from hot to cold, or the blend door actuator isnt functioning right.

Aug 10, 2009.