Defrost at all times

[Bigsmoothe49]

All of a sudden all of my air blows out of the defrost, no matter what I have the selector on. Isn't my 4wd controlled by vaccuum? If so I checked it and it appears to be working fine. Any ideas where I should start to check before I spend too much $ for a diagnosis?

 

[blacksnapon]

Your 4x4 works? If so, there probably is a vacuum leak or restriction from the tee to the hvac head. Its engineered to default to defrost only if theres a problem with the vacuum source.

 

[GHoss]

This happened to mine turned out to be the vacuum pump. The heater will only blow through the defrost. Your auto hubs will not lock in till the vacuum pump is replaced.

 

[Bigsmoothe49]

Ok so I was wrong about my 4wd...Had to lock the hubs in the worst snow in South Carolina in about 10 years (8") How do I check the vacuum pump and where is it located?

 

[blacksnapon]

Ok so I was wrong about my 4wd...Had to lock the hubs in the worst snow in South Carolina in about 10 years (8") How do I check the vacuum pump and where is it located?

On a diesel, its on the passenger side fenderwell on top. When you turn the key on, it should be running.