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Stuck in defrost

6K views 12 replies 5 participants last post by  bigb 
#1 ·
My vents are stuck to defrost position no matter what i chose. Ive done some research and looked at my pump. It turns on when power is applied. I pulled the vacuum hose running to the firewall and heard a hiss from the vacuum pump side. I have warn hubs and dont know if they're vacuum operated or not. I always manually move them. I did have a free flying line that i repaired on the passenger hub. Still no luck. Any help is appreciated
 
#2 ·
Blend door could be stuck.

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#3 ·
Follow the vacuum hoses up from the knuckles all the way to the pump. Then plug it off at the pump. Also there is a vacuum connection right under the glove box that sometimes gets disconnected.
 
#4 ·
Take the lines off the vacuum canister and plug them and see if the pump fills it and shuts off. If yes then reconnect the cabin vacuum line and see if it runs and shuts off if yes hook up your esof valve and see what happens. My esof valve was leaking so I had no vacuum and stuck on defrost.
 
#6 ·
Because you have warn hubs you don't need the vacuum to have them engage. I would do the vacuum first. Much easier to get too.
 
#7 ·
The esof valve can still be leaking no matter what hubs you have and the 4x4 will go in cause it is driven by power not vacuum
 
#10 ·
Welcome to the forum, I am just up the road from you in Tucson. I never heard of a 99-03 having an egr valve, is it a Cali truck or something?
 
#11 ·
There is no egr valve on a 7.3.

Most likely the esof solenoid.
 
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