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Heater control stuck on defrost - 2000 F250 Powerstroke

16K views 5 replies 4 participants last post by  tjc1989 
#1 ·
My heater control is stuck on defrost on my 2000 F250 Powerstroke, or rather the control on the dash turns OK, but the results are that it only blows air on the windshield through the defrost port. I can't get it to change air output to floorboard or dash ports. Other controls such as temperature control and fan speed work OK. Any ideas what is wrong and how to fix it? Thanks in advance for any help.
 
#2 ·
That's usually a vacuum problem. Either the little pump on the passenger fender/firewall under the hood has gone bad, or a line has fallen off somewhere, or (in a lot of cases) there's a cracked line down near the ESOF hubs that is letting all the vacuum escape.

The default position of the vacuum-operated flaps is defrost.

Duncan
 
#5 ·
#6 ·
That was it. No vacuum. I checked the pump and not working, and no voltage to it. That left a fuse, which was the culprit. So replaced it and its working OK now. Thanks again. By the way, mine is a 2WD and thats why I wasn't familiar with the ESOF term. /ubbthreads/images/graemlins/laugh.gif
 
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