Hi, the heater in my 96 works and heats up, the fan runs, but the 'doors' that allow the heat into the passenger compartment won't open! So, I've just barely got any heat at all in the interior of the car, very little defrost, my windshield/windows fog up and freeze etc.. With the temps here at below zero and/or just a little above, I'd like to get those 'doors' to open. This is my only transportation ATM, so I gotta get it fixt. I've got the dash controls exposed, and it is a vacuum selector switch that controls the different 'doors' - i.e. upper, lower, defrost, floor, etc., but according to O'Reilly's Auto Parts, the only replacement switch is electrical. They checked for the year before and the year after, they only show electrical selector switches! They tell me that 'usually' would mean that the vacuum selector switch is no longer manufactured. This same selector system is supposed to work for the AC, but that wasn't necessary this past Summer as the heat wasn't too extreme, so I kept procrastinating and now I regret that decision (or lack thereof ;>)).

Does anyone have any ideas on how I can test this vacuum switch to determine how to open the 'door' that will bring heat into the cab? I've looked for vacuum diagrams online - AutoZone has some good ones, but they don't show the heater controls, only the engine under-the-hood diagrams.

The reason I know it's a vacuum selector switch is that there are about 6 small hoses running to the back of the switch and no wiring. The picture that shows on the O'Reilly parts computer is totally different. I'll have to buy a vacuum tester gauge to see if any of those 'hoses' have vacuum to them, but how would I know which of the other hoses is the correct one to open the 'doors' for the heater? (I'm assuming this will turn out to be a lot of trial and error, but I'm hoping someone has a possible shortcut to my dilemma.) Any suggestions or advice will happily be appreciated!
TIA, jimk

 

one of the more common problems is the actuator that moves the blend door,you might be able to access the door from behind the glove compartment

 

Thanks for that advice, but I don't even know what a 'blend door' is or looks like ... so, what should I do now? ... figure out how to remove the glove compartment? (I know, most of them are false compartments and when you remove the compartment itself, there is 'stuff' behind them), just asking! If it's anything like my Ford Falcon, there are a few screws to remove and the (cardboard) glove compartment will come out. Any advice as to what I should look for as far as the 'blend door' or the 'actuator' ? How would I activate it, would it have a vacuum hose running to it? etc.?
Somewhere I have a vacuum gauge tester around, so would that have vacuum to it or would it have pressure? And how much vacuum/pressure should it have to open those 'doors'?
NOTE: I DO appreciate the advice, not mocking! I just want to know what I'm doing as far as what the blend door and the actuator might look like, how to make them/it open/close the 'doors', etc..
Thanks,
jimk

 

if you google your problem many pictures/solutions will appear.it's fairly common on mid 90s gm.