I appreciate your advice, the more I look into it I am thinking it is the GEM, my overhead display went out a while ago and i have seen some info that may be linked, as you said before power does go to the 4x4 switch from the GEM and I'm not getting any. Here is another question, does the GEM have to be programmed by the dealership if i order one online?

Thanks again!

 

https://www.ford-trucks.com/forums/1...-question.html

Everyone thought it was my GEM. Worth a check

 

[ does the GEM have to be programmed by the dealership if i order one online?

Thanks again![/QUOTE]
Sorry I really don't know. I hope you don't need one. Mine was just the connection. Maybe someone reading this knows.

 

I heard they don't make them anymore. I think you can take them apart, clean the contacts etc also.

 

The first things to check are the vacuum hoses going to the front knuckles, they are known to break and leak.

 

I have the same issue with it switching on the fly. Vacuum pump operates and is functional. I did find a large melted spot on my vacuum tube part number 3C124 (the plastic ribbed tube). However, my air vents don't switch from front to defrost like others have. I'm convinced the melted spot on the down tube is the reason mines isn't locking. I wish I could upload the photos here but its not letting me.
http://apps.pixlr.com/express/?copy=...8.JPG&type=jpg

 

put soapy water on it or submerge that part.

 

EX,

I wish I could get the pictures on here. The tube is worn through as in completely severed. What I was trying to relay was that since I have that obvious leak, my vents for my AC / Heat does not change when I activate the 4x4 switch as others are reporting. I had read that was a good way to tell if you have a leak. Which why I didn't think I had a leak because I did not have those symptoms. I just followed the tube down and found it was melted completely.

 

It could be that the tube that is severed by melting is maybe melted shut or was melted so that it wasn't losing vacuum but now since your AC/ Heat control doesn't work right it is leaking. I think I read that when there's a vacuum leak the heat will only come out the defrost vents.

 

Dave,

No problems with my AC or Heat...sorry should have clarified.
I was saying my vents don't change when i use the 4x4 switch like a lot of others experience. The only way I knew I had a 4x4 error was trying to get my truck up my muddy driveway and it wouldn't lock in by the switch...made me do some digging (no pun) and look into my trucks 4x4 system and found the tube completely melted open so no vacuum what so ever.

 

Was that the problem? Is it fixed?

 

While doing calls in Berryville VA, John Rumaker met with Dave Fulton of Round Hill “Exxon” Service Center. Upon entering the bay, John noticed a Ford Axle end seal still in the bag. He asked the lead tech about it who confirmed the seal needed to go in but they were putting it off till later due to the high level of difficulty of putting them in. Upon seeing the National 710825, he became very interested. The ease of installation was highlighted and very well received. John told the tech if he had problems installing the Ford seal to call him and he’d come back with the National one. It happened and John came back after hours to help install the National seal. Long story short, the vehicle was fixed, the installer was impressed and grateful, but most importantly, the owner Dave became a loyal F-M products customer.<o></o>
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You won't lose the HVAC system (defaults to defrost) unless the SOLENOID itself is venting to atmosphere all the time. A broken line, leaking seal, whatever, usually doesn't make it default to defrost.