Can't Control Heater & Defroster

courtesy of Bob, The Auto Answer Man

Hello Bob,
I have a 1996 jeep Grande Cherokee and my problem is when you accelerate hard and have the heater on it automatically switches to the defroster. After you let off the gas it then switches back. I hope you can help me and thanks for your time.

The direction of air flow on most cars is controlled via vacuum. Upon hard acceleration the engine's vacuum drops. This may be causing the car to go to default heater control (which is probably defrost). There may be a leak or a crack in a hose or a bad vacuum diaphragm that controls the air flow.
Good Luck!
Drive Safely!
Bob, The Auto Answer Man

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