what will cause my air conditioner air to transfer from front to deforst outlet without changing reostat setting.
While driveing, my aircondtioner air will transfer from the front ducks to the deforst ducks under the windshield and sometimes will stop all together. I noticed that the reostat knob will go past off and past the last setting when turning counter clockwise also.
There is a vacuum hose that goes from the back of your A/ C & heat control panel to the intake manifold. There is supposed to be an in line check valve that prevents this. Yours is either missing or faulty. It looks like a small round disk with vacuum hoses attached to both sides of it. It's usually white in color too and near the firewall. HTH. -Jim
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