Blend Door

Replacement HVAC Heater Blend Door

The heating, ventilation, and air conditioning (HVAC) blend door is used to control the ratio of hot and cold air, allowing the driver and passengers to adjust the interior temperature of the cabin. The blend door is a small panel inside the heating and A/C system controlled electronically or using vacuum by the blend door actuator. The blend door actuator regulates the amount of hot and cold air flowing through the blend door and is controlled by the temperature selector in the passenger cabin. Over time, blend doors and actuators may wear out or develop electrical problems, preventing them from operating appropriately. When this happens, it can cause poor temperature control, an inability to change from hot to cold air, or inaccurate temperature selection. If you notice problems with the air flow or temperature, check the blend door actuator for bare or broken wires. If the blend door actuator itself is damaged, you may also hear clicking or other noise under the dash when changing the temperature selector position. A failing blend door may produce similar symptoms, as it may be binding during operation. Some temperature blend door actuators also require reprogramming or a system reset to calibrate them appropriately, so ensure you determine the proper steps to replace your blend door, blend door actuator, and more in your service manual. For your next HVAC system repair, shop O'Reilly Auto Parts, where we carry replacement HVAC blend doors and other components for a complete repair.