Pontiac Repair: ac&heater trouble, vacuum gauge, foam seals

Question
QUESTION: i have a 92 firebird v6 3.1 when i select ac or heater i get no air out of the top vent panel, but you can hear the fan blowing at all speeds,the sound comes from the bottom ducts.

ANSWER: Hey Wilbert:

It's one of 2 things either a vacuum leak going to either the control head or to the actuator for the mode door in the HVAC Box. Usually on a GM car if you loose vacuum or have weak vacuum all the air defaults to the defroster. You will have to take a look on the side of the HVAC box and see in the mode door moves when you switch modes from floor to vent etc. You may want to put a vacuum gauge on the hose fo the actauator and see if it's missing vacuum or just the actauator is leaking. The last thing could be a door that is jammed up in the box. Over time the foam seals on the door become dry rotted off and they fall off and bind up in the doors. Good luck :}


---------- FOLLOW-UP ----------

QUESTION: I CHECK VACUM (GOOD)DOORS OPEN,STILL NO AIR,SO I REMOVED BLOWER MOTOR AND HEATER CORE COVER AND BLOWER SWITCH.AT THIS POINT I TRIED BLOWING AIR THROUGH THE EVEPERATOR WITH NO LUCK,CAN THE EVAPERATOR BE MY PROBLUM.

Answer
I doubt it if the temp door was on hot the air doesn't go across the evap core I do belive on this car. I stil lthink there is a issue with the mode dore that is the door that direct the air out of the differnt vent settings. if you get air flow out on the bottom the air is blowing across the heater core but no air out the defroster then ther is an issue with that doow or the linage for it or the actauator. Without seing it it's hard to say exactly what the issue is but That is my best guess.