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Discussion Starter · #1 ·
i have a 06 f250 lariat the front hubs wont engage in the automatic postion but i can out them in the lock postion and they work fien i was told that i might have a vaccum problem also my a/c stops working if i back up a hill it goes straight to defrost could that have something to do with my hubs also not enough vaccum need help
 

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I just went through this on my 07 F250. I was having the defrost only-no vent problem. I learned on the forum to trace each vacuum line from hub to pump and make sure there are no disconnects or breaks/cracks in the lines. Up top at the pump, find the grey hose leaving the pump and trace it to the heater hose and make sure it is connected. I got excited and ordered a new pump before troubleshooting, and my grey hose was disconnected.

If all your lines are good, start the truck and disconnect the grey hose at the heater hose, put your finger over the grey hose and see if you feel a slight suction. You should. If you don't, make sure your vacuum pump is getting voltage. If all the above fails and the pump is getting voltage, order a new pump off Ebay. They are plentiful at $50-$75.

Hope this helps.
 

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I wish ford would get away from using vacuum for 4x4. I always just lock my hubs in when I want to put it in 4x4. On my 2000 I actually replaced the hubs with warn hubs and blocked the vacuum lines off all together. It causes a lot of problems with the half ton 4x4's as well. These leaks can be a pain to diagnose, but check all the obvious stuff first.
 

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I have the same issue. Auto 4X4, defrost comes on. Lock 4X4, works. I found the vacuum leak. It's coming from the little vac hose that comes from the solenoid and the into a little nipple that goes straight down to the wheels. I was able to plug the bottom vac hose into the solenoid (bottom) and hook up a small hose from the solenoid (top) to the wheel vac line. Now the fan does not go into the defrost when I turn the knob in 4X4. But the truck does not go into 4X4. Any ideas?
I hope I am clear on what's going on?
 

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Well I have narrowed it down more. I put a hose on each of my wheels and sucked on them. Yes sucked on them. The wheels dis engage the axle. So I put a hose directly on the wheel and to the vacuum solenoid and did not get wheel engagement. Then this seems to be my vacuum solenoid that is not working, right? Anyone have a part number or price?
 

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I have the same problem, my driver side i can move from auto to lock manually, its a little tough, but the passenger side i cant move unless i use pliers. I switch the truck from 2wd to 4 hi and they dont have locked....anyway to service these and grease them up? also when you select 4hi are the hubs suppose to move from auto to lock?
 
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