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Q: Heat and air controls broken

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The heater and air conditioning controls do not work right. All come on as defrost.

Hi. This can be caused by two things. There are actuators or motors under the dash that operate doors in the vent system. These door direct air to the different vent locations. The actuators can be ran by vacuums or they can be electronic. If they are vacuum operated, the vacuum line might have come off causing a leak. The default setting in this case is the defrost, so that is where it blows from. If the actuator is electronic and fails, the same will happen. Depending on the diagnosis, dash removal might be necessary to access the actuators. A qualified mechanic, such as one from YourMechanic, can inspect the AC for proper operation and replace any failing components.

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