I just bought a 1996 Chevy blazer. broken air vent cover.

It should be on the inside cover of the fuse box

the idea of the switch is run on vacuum and is not making contact with the switch it self either worn contacts in the switch itself **** as an obstruction as well or the vent door is stuck in just that position either behind the glove box or the ash tray are the vacuum lines one of them may be pinched off or the door needs a bit of help until you can free it up

see if this helps
paul
www.carburetorexchange.com

Is it your ventilation not switching, or your blower motor not blowing air?

here is a piture of the seed control resistor module, it goes into the air duct near the blower motor.

cabin air filter is under the golve compartment or under the cowl vent cover / Please rate my response thank you very much

NO, it's kind of tight, but it's not that bad. You do need to remove the torque converter cover, and slide/rotate it as much to the driver's side of the vehicle as possible.

relay or resistor

i would say its in the dash unfortunately you will have to pull it out to inspect.

it takes a special puller to remove the steering wheel. the air bag just pops out with a release tool in the release hole on the side of the steering wheel