2001 f-250 4x4 ....my vents inside the cab are stuck on the defrost position both my heater and AC work but its always defrost...is this vacume pump or could it b fuse??

 

Your lucky.. this is an easy. You have a vacuum leak, most likely form one of you 4x4 hubs..

CHeck the vacuum lines that run down to your hubs, it may be disconnected, or a hole in it..

Sorry, are you in 4x4??

 

The entire system (by Federal law) must default to "defrost" whenever something fails.

In this case, you either have no vacuum (pump usually), or you have a vacuum leak (lines usually).

Most common leaky lines are in the wheel wells that feed the vacuum-operated hub locks, assuming you have ESOF (Electronic Shift On the Fly).

I replaced those on mine with small fuel line, as it holds up better in the long run. A couple of tie-wraps keep them tight on the ends.

Pop

 

I have heard that those blend doors have an issue with the rod coming off inside. If all your vaccum lines check out might be worth having a look.

 

Thanks guys il check it out and ya my 4x4 is ran off the switch

 

so ended up my vaccume pump only comes on when you hit it with a pair of plyers so...new vacuume pump..prob not fixed...the soliniod that sends vacuume to my hubs is stuck open it seams and letting vacuume leak by..so i unplugged this and actually wedged two sticks into the vacuume hoses to bypass autohubs for the time being....i still believe i have a leak in a vacuume line up to my cab though because i have got my vents to work but when they do work its short lived...also checked the vacuume reservoir by tapping the vacuume pump to the resevor only and it functioned correctly so i believe it has to be between the cab and resevior..mayb ,mayb not