Posts Tagged: mode door

What is a mode door and how do they fail?

Bad mode door symptoms A mode door is used to direct the flow of air in a vehicle, or it’s “mode” of operation. A typical heater box may use several doors and  actuators to direct the flow of air to the windshield defroster, dash vents or floor vents. The actuators on late-model vehicles are electric motors with position sensors that tell the HVAC control head the exact position of the mode door. On older vehicles, carmakers relied on vacuum motors to change the doors. On still older vehicles, the doors … Read More