ac/heater question

**stump0331** · #1 (**permalink**) 03-15-2007, 05:00 AM

got a buddy who has a problem with his 99 f150 v6 and the ac/heater.

he said when the heater OR the AC are set, at any given time it can switch to the opposite setting on its own.(ex. driving with AC on it will just all the sudden switch to heat) he said it does this at all fan settings. he suspects its a vacuum leak. but he isnt sure on how to locate it.

HELP!!!!!!!!!!!!!!!

**stump0331** · #2 (**permalink**) 03-22-2007, 05:18 AM

bump bump bump

**Dave** · #3 (**permalink**) 03-22-2007, 05:19 AM

Im gonna say vac leak or bad switch

**pipelayerjdh** · #4 (**permalink**) 03-22-2007, 03:15 PM

On some of the newer trucks the heater control valve is located under the hood in the heater hoses. I would start there and see if it had a vac. leak. Those valves also go out often. I don't know if the 150's have 'em, but the newer rangers and explorers have 'em. Hope this helps?1

fishingjred73 · #5 (**permalink**) 03-22-2007, 03:27 PM

Could be someting electrical. Just got rid of wife's 97 grandprix that would blow cold air out of the right two vents while the left three were HOT. GM had some kinda module

under the dash that wasn't sealed and would make the hvac controls go crazy.

**djdieseltech** · #6 (**permalink**) 03-22-2007, 03:48 PM

Quote:

Originally Posted by stump0331

bump bump bump

your blend door actuator or your blend door is cracked at the bottom.

dj.

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