I have a 2012 Chevy Malibu. When the AC is on it blows through the defrost vent instead of the front. What causes this? Never heard of this happening.
You likely have a vacuum issue. Probably a hose is off the VENT vacuum motor, or there is a leak at the vacuum distribution plug at the back of the control head. Or there could be a broken vacuum line, or a bad vacuum motor for the vent function.
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