Alright guys, this is wierd. I put my truck in 4x4 high today and the air conditioning changed from max A/C at the vents to a/c defrost. What gives? It goes back to blowing through the vents in 2 wheel drive, but as soon as it goes into 4 wheel drive it changes. Changed back and forth several times and each time I got the same response. Any thoughts?

 

Auto hubs? You probably have a vacuum leak in the hub system.

 

not so wierd! both systems ahve the vacum pump and lines in common. you have a vacum line going to one of the hubs unhooked or cracked. start at each wheel and tarce the vacum lines. you will find your problem there

 

Yup vac leaks. Welcome to the club.

 

thanks for the help fellas

 

I had the same problem. I think my problem was the hub or hubs leaking.... not the lines going to them.
Changed out the factory auto locking hubs to Warren Premium Manual Hubs.
Plugged the vac lines off. No more problems with the A/c vents defalting to the defrost vents due to a vacuum leak.
Only thing now is that if I anticipate needing the 4x4.... must first get out and lock the hubs..... However.... I now have a 2x4 low range ..... just don't lock the hubs and switch the **** to 4x4 low.

 

My truck does the same thing. It doesn't really bother me. I always manually lock the hubs anyways just to be sure they are locked when I need them. Should I be concerned that this phenomenon is adversely affecting other functions/parts of the truck? Thanks.