HVAC not switching position

[Renegade7.3]

As most of you know. our trucks still use vaccum to control the switch as to where the air from our HVAC comes out of in out trucks.

Now mine is not working, i know my vaccum pump is running i hear it when i turn my key on. The vaccum lines i can see look fine under the hood. I cant really see any under the dash.

Has anyone had this problem? What did you do to fix it? It really sucks just having the heat on defrost all the time cause thats where it defaults to.

 

[Rupp250]

Check the lines that go to the hubs, pretty common for the to crack down there.
I just removed the line from inside the engine bay and plugged it so there wouldn't be a vacuum leak. Works great now. I just get out to lock the hubs.

 

[Arisley]

There is also a tee under the glove box that will get hooked by a foot and disconnected.

 

[Renegade7.3]

thanks ill give it a check as soon as i head back out to the garage and report back to what it was if i can find it lol

 

[83f350]

when mine went there was a fitting that had cracked on the passengers fender. fixed that and it worked fine

 

[Renegade7.3]

well just an update, it was a bad vacuum pump. it would switch just after ten min. of pumping lol