1993 Ford Aerostar

Electrical problem
1993 Ford Aerostar 6 cyl Two Wheel Drive Automatic 161000 miles

Hello I have a 1993 ford aerostar 3.0L. When my engine is running it idles fine. As soon as I turn my heater on to floor, vent, or defrost within a second or two my idle jumps from curb idle to high idle. This happens continuously as long as my heater is on. If I turn the heater off the idle is fine. (Ex. Up, down, up, down, updown etc.) I think it might be a electrical issue. Any suggestions would be great. Thanks
January 20, 2010.

The defroster turns on the AC which should increase the idle; however, your problem seems to be releated to the idle air control (IAC) or the throttle position sensor (TPS). Has the check engine light come on?

Let me know.