Chevrolet Astro Forum : “Changed alternator...now only defrost”
Changed alternator...now only defrost
I recently changed the alternator in my van. Since then, air will only blow from the defrost. Blower fan, a/c, and heat all function. Any assistance in helping me isolate what I've done to cause this would be greatly appreciated.
Alternator change is most likely not your problem. Sounds like you have a problem with the blend door inside the climate control system. Probably just coincidence that it happened at the same time as the alternator change.
the heating system on almost all vehicles defaults to defrost ( so you can see in winter) there is a very very good chance the vacuum supply line to the heater controls was broken kinked disconnected during alt r&r inspect under hood very close listen for slight hiss with engine running find vaccum leak find problem
