I'm having an issue with the heat/air system. All of a sudden I can't switch the vent system. It is stuck on defrost. It won't switch to floor, vent, etc. I have defrost and off. I looked at it and if I'm not mistaken it looks like it runs off vacuum. Hoping someone can aim me in the right direction.
Also coolant temp won't come up which I guess is a stuck thermo. Both happened at the same time so I figure I would throw it out there in case there related.
Thanks for the help in advance.

 

A vacuum leak will cause the climate system to default to defrost.
First step is to look where any recent work has been done and a vacuum line might have accidentally been disconnected.
Very common for them to get disconnected in the fuel filter area while changing the filter.
Another common leak is under the driver's side battery where acid tends to rot the vacuum line to the cruise control.
Easy way to tell if you have a vacuum leak is to run the engine, shut it down for five minutes then disconnect any vacuum line.
If it doesn't hiss you have a leak and need to start searching.
A system without leaks will hold vacuum for hours if not days.

 

Check the vacuum line that runs above the turbo...mine came loose from the loom and got to close...melted it.

 

I love this group. The rubber elbow on the block is dry rotted and the vacuum line came out. I repaired temp. and all is well. Thanks for all your help.

 

I did that to my dually when I swapped turbos the first time. It was funny, because I had the A/C going, and my windsheilf began to fog up in 30C+ weather.