The HVAC air outlets in my 1998 Chevy Astro AWD passenger Van will not change from defrost to dash to floor, etc. All of the air is coming out of the defroster and will move to come out of any other outlet. The switch on the panel will turn the system off and turn the AC on, but does not operate the air vents. Is this maybe a vacuum or an electrical problem? How can I fix this myself without taking it to a mechanic?

Randy VL, February 2008

I had the same problem, it was a vacuum leak ,we were unable to hear a hissing noise from under the hood but take off the cover of the engine between the driver and passenger seat. After you start your car listen for the leak, I guarantee it's there. Mine was very hard to hear but I found it and it was worth not having to pay someone else to do it.

mom, July 2008

Most vehicles, including yours, has a 'mode door' that has a vaccum actuator to make it move. Either the vacuum is not getting from the engine through the ac controls to the actuator, or the actuator itself is bad and is leaking vacuum.

Poke around under the dash and listen for any hissing sounds...maybe you get lucky and the vacuum hose just fell off or split at the end.

Earl, February 2008