heat only blows through defrost
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Senior User
Joined: Apr 2006
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heat only blows through defrost
my heat only blows through the deftost vents it dose not matter what setting I put it on thay all ack the same. I had heard that it could be a vacuum line but I thaught that diesels didn't have vacuum. I am still new to this deisel thing. any thaughts?
Cargo Master
Joined: Apr 2004
Posts: 3,162
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From: Vilonia Arkansas
You have an electric vacuum pump on the pass.side under the hood on the inner fender . If you pull the glovebox out the vacuum lines are right there in front of you .When there is no vacuum it defaults to defroster.
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Senior User
Joined: Apr 2006
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when should the vac pump come on? mine is not turning on at all mabie it is a fuse I tryed looking for the fuse in the manual but nothing says 'vacuum pump' dose anyone know which fuse controls this? thanks.
Elder User
Joined: Apr 2004
Posts: 797
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From: Wickenburg, AZ
It should come on when you first switch the key on in the morning. A nice, steady purr for a few seconds.
There was a TSB on the vacuum pumps, so you might want to check it out on your top bar here at FTE.
There was a TSB on the vacuum pumps, so you might want to check it out on your top bar here at FTE.
Junior User
Joined: Sep 2003
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Vacuum pump motor is bad or line is off. This happened to me and I found out the defrost position is the factory default when no vacuum is present.
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Senior User
Joined: Jan 2004
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From: MN
What did you find out? I also am stuck on defrost and my shift-on-the-fly does not work. How do I trouble shoot this?
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Of the next Riffraff East
Joined: Oct 2004
Posts: 8,679
Likes: 2
From: Concord NC
Originally Posted by bkvanbek
What did you find out? I also am stuck on defrost and my shift-on-the-fly does not work. How do I trouble shoot this?
Hook it, I'll pull it.
Joined: May 2007
Posts: 15,037
Likes: 4
From: Grand Lake, La.
You could also take both lines off the hubs, plug the lines then start truck put ac on, switch to 4x4. If ac goes not go to defrost, you have a leak in one of your hubs. Then put 1 line back at a time and repeat the test to find which hub is leaking.
Of the next Riffraff East
Joined: Oct 2004
Posts: 8,679
Likes: 2
From: Concord NC
Check the lines like Rick suggested to eliminate your hubs. If they check the problem still exist, and you know your lines are good, then it may be a bad solenoid or maybe even a bad vacuum pump. Unplug your line from you vacuum canister to the solenoid and plug it off. See if your heat defaults to defrost. If so, you have eliminated you ESOF system. If you heat goes to defrost all the time and not just when you use your 4x4, you have a line leak between your vacuum canister and the blend door in the cab. Sounds like you have some tracing to do.
Of the next Riffraff East
Joined: Oct 2004
Posts: 8,679
Likes: 2
From: Concord NC
Just re read your first post and you did say it blows all the time, this means you have a major leak or a blown fuse to your pump. Maybe even a bad pump. The pump is mounted on the passenger side fender and you should hear if run for a few seconds after you turn the key to on. Stand outside with hood up and have someone turn key on and you will hear it if it is working.
