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2002 Chevy Malibu AC/Heat Issue


My 2002 Chevy Malibu A/C / Heater is being odd as of lately. No matter what setting I put it on (Defrost, Front Vent, Floor Vent), the air blows out of all vents, strongest in the feet area. Some people have said my Blend Door is stuck, which makes sense I guess since the air gets hot and cold when coming from all vents, its just a weak flow since it is not in a concentrated area. Do any experts out there think this is what is wrong with my car or is it something else. The fans work on all speed setting, its just the location of the air never changes regardless of the setting.

Thanks in advance for any help!

There is a little motor that diverts the air and it needs replacing.

Do you know what that motor is called?

The problem isn’t with the blend door. The blend door controls whether hot or cold air enters the passenger cabin.

The problem you’re having is with the mode doors. And there are three of them with their own vacuum actuators.

These are the defrost mode door, the dash mode door, and the floor mode door.

The vent control module directs or cuts off the vacuum to each of these actuators depending on the mode selected.

The odds of these three mode actuators failing at once are nil. So either no vacuum is being supplied to vent control module, or the rotary valve within the module that directs the vacuum to the actuators has failed


I forgot that Chevy still used vacuum operated actuators into the 00’s. My 95 Dodge motor driven actuators and my 99 Toyota does too.

So if I replace the part you listed, then it should start to work again or is there another way I can fix/test it out? I’m by no means an expert on cars.

I guess also is this something that can be done by anyone or is a professional required? Based on what you said, I looked it up, and some people say to test the hoses for a vacuum. But I don’t even know where to find these hoses, etc.

The vacuum source for the module comes off the throttle body on the engine, thru the firewall, to the vacuum check valve, to the vacuum reservoir under the dash, and then to the module.

You could check under hood to see if you can find a disconnected/broken vacuum hose on the throttle body.

I nothing is found at the throttle body, then the module needs to be removed from the dash so see if vacuum is being supplied by the two hoses on the back of the module, and if there’s a problem with the vacuum hose manifold on the back of the module.


It’s actually good news for you OP that your car sports a vacuum operated blend door mechanism. Those are more robust than the new stepper motor technology, at least from the reports we see here. As said above, the first thing is to make sure the vacuum source is reaching the controller. I’ve never done it myself. Both my cars works that mechanism by simple cables and have never failed – makes one think, eh? Anyway, for you I think that means there’s a vacuum hose from the intake manifold going through the fire wall, and that’s the first place where you have to test for vacuum with a vacuum gauge.

Still, even though it should be fairly easy to do, trying to do this yourself without the proper instruction for your car is sort of like trying to drive through a strange city you’ve never been in before without a map. Not advisable in other words. Try to find a write up of the procedure first.

It’s possible also the vacuum is fine, the controller is fine, but something is jammed under the dashboard. Sometimes you have to use a flashlight and mirror to look up under there, looking for a broken cable or spring or something. Best of luck.

Edit: Those vacuum reservoirs (bottles) and connections to them seem to be a common problem.

It’s usually the vacuum elbows and hoses that rot and split open

The plastic vacuum reservoirs sometimes get damaged in collisions and when some doofus gets careless and cracks them

Of course, it is 12 years old. Stuff breaks. The system needs to be checked between the vacuum source at the throttle body, through the mode switch, and to the servo motors.

I also had an '02 Malibu with exactly the same problem. I popped the hood there staring me in the face was a broken vacuum line. The fix is super easy. Just get a 2 or 3 inch piece of rubber vacuum hose (about 1/8" I.D.) and slide each piece of the broken plastic vacuum line into it. If it’s a tight fit you don’t even need to clamp it.