4WD and Defrost!!

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Apr 24, 2008 | 04:46 PM

gopher74

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4WD and Defrost!!

I have a strange problem here... I recently selected 4wd on my f250 and the lights come on I hear the "click" but nothing the rear right spins in the mud. After some serious disgust, I get the truck back home and try it in the driveway. As soon as I select 4L the AC goes straight to windshield defrost. It will not change regardless of selection until I turn off 4L and turn the AC off. I tried this again with the same results. I figured its a vacuum issue but where??? Any help out there would be great.. thanks guys for this site...

Apr 24, 2008 | 05:14 PM

IB Tim

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Apr 24, 2008 | 05:39 PM

zx250

Of the next Riffraff East

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From: Concord NC

Yes it is a vacuum leak. It is probably at the hubs, you can put the hubs in lock and plug the vacuum line at the solenoid if you need to. What year is your truck and I'm guessing it's a diesel.

Apr 24, 2008 | 05:40 PM

wlihntr

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From: colorado

you have a vaccuum leak somewhere the hubs use vaccuum to lock in and the HVAC controls also run of vaccuum. the defrost is the default if the HVAC controls dont have enough vaccuum to operate. you coukd have a bad vaccuum pump (under the hood on the passenger side fender). sometimes the lines to the hubs will leak and you can also check under the glove box there is a vccuum hub there that often gets damaged..