Defrost (Heat) Comes On By Itself - JeepForum.com
 
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post #1 of 3 Old 04-03-2006, 11:15 AM Thread Starter
UnDeR EsTiMaTeD
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Defrost (Heat) Comes On By Itself

Yesterday I took a drive out to the desert where the outside temperature was around 100 all day. As I would climb a few inclines, the defrost would come on all by itself. It was blowing hot air from the defrost vents only. It would stop once the engine didn't have any kind of load. It didn't do it around town or cruising. It only happened as I would put load on the engine. What is causing this?


1994 Jeep Grand Cherokee 4x4
4.0L - I6 @ 200k & Counting!
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post #2 of 3 Old 04-03-2006, 11:18 AM
ArloGuthroJeep
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A leak in a vacuum like OR you need to place a one way valve in your HVAC control lines to prevent it from switching on you...Someone will chime in with exactly what kind and where the valve goes.

'04 WJ, 6" Clayton LA's, 242 SYE, 35" BFG MT KM2's, 4.56 gears, & D44a locked
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post #3 of 3 Old 04-03-2006, 11:35 AM
FPKites
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Here you go - sounds like you need the check valve if it does it when under load. If you had a leak, it might ONLY blow out through the defroster.

http://dodgeram.info/tsb/1996/24-01-96a.htm

Jim Karlin
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