Hey I noticed in my Mustang that when I change the climate controll to come out of a different spot it only comes out of the defrost it seems like. The controlls run on vaccum correct? So do I possibly just have a vaccum leak somewhere? Could you all point me in the direction of fixing this? Thanks.

 

Look for a small tube going though the firewall. That seems the be where they can leek.

 

Is that the thing that is most likely causing the problem?

 

Probably

 

yes. check at the tee connection above the brake booster. you'll see A/C printed on the tee... follow that line. it's probably broken somewhere. if not, check under the dash/glove box to make sure the vac line connector is still connected