We're having a problem on our 1984 Mustang project car regarding the heater and air conditioning controls. Regardless of what settings we use the air only comes out thru the defrost vents. I'm sure this is a vacuum line problem but just not sure where those particular vacuum lines are located. Any help would be greatly appreciated.

 

This May be Helpful.

KC

 

Thanks Kevin,

Turned out to be the mode selection switch. Replacement part was available from Motorcraft and was cheap ($24), so I ordered it. Everything else checked out so I should be good to go after this.