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AC/Heat control problem

Hey guys,

I have a 97 Chevy Lumina. About 2 weeks ago, I noticed that the control knob for my AC and heat that selects where to blow the air (up through the defroster, through the dash, on the floor, etc.) has stopped working. I can hear the fan running and can adjust the force that it blows. I can also adjust whether it blows hot or cold air. The only knob that is not working is the one that adjusts where the air comes out at. It’s stuck just blowing air on the floor and through the defroster.

Do you think that this would be something that could be fixed by changing a fuse or a circuit breaker or a relay, or am I going to need to visit my local service station?

Thanks for your help!


The ventilation system in your vehicle utilizes a vacuum solenoid control module. When you want defrost and set the knob to that position it energizes a solenoid in the module which directs the vacuum to the vacuum motor for the defrost door in the vent system.

You might want to check if this vacuum control module has failed.


Also make sure that you are getting battery power to the control module and that the vacuum line to the control module is intact.