What is a Blend Door Actuator?

Figure 1: A blend door actuator.

Blend door actuators, also known as Heating, Ventilation, and Air Conditioning (HVAC) actuators, control the position of the vents and the air flowing into the passenger area of the vehicle. They move the vent door, mixing hot air with cold air to provide you with desired temperature. Most vehicles have two blend door actuators, one on the driver's side and the other on the passenger's side.

Basics about a Blend Door Actuator

A blend door actuator is an electric motor with sensors connected to the vehicle climate control system. It is located in the air conditioning and heating system of the car. When you turn the dial to increase or decrease the temperature or the airflow, the signal goes through the blend door actuator. It also controls the defroster and other vents.

A blend door actuator is a miniature plastic box, inside which are plastic gears, electronics, and a plastic case that holds everything inside.
Blend door actuators control the temperature and the airflow in the vehicle. If your vehicle only releases cold air, or you can't change the airflow, it may be due to a faulty actuator. Sometimes, fixing such issues requires recalibration, and sometimes you need to replace broken parts.

Figure 2: A car HVAC actuator consists of eight components.

The Location of the Blend Door Actuator

The door actuators are accessible by removing the glove box and under-dash trim panels. The alternating current (AC) actuator is located under the dash and connects to the air distribution door in the HVAC box. Doors can control warm air/cold air mixing, recirculation/fresh air control or dual zone separation. The motor can move the door to many different positions, or to just two.

Workings of the Blend Door Actuator

The air blend door actuator is a small electric motor with plastic construction. In this unit, a door position sensor is also integrated, which sends information to the climate control computer. Therefore, this actuator controls the temperature and air direction according to the settings.

Figure 3: Position of air conditioning servo assembly in a car.

What does a Blend Door Actuator do?

Blend door actuators are part of a vehicle's HVAC system that regulates airflow and temperature in the vehicle based on settings. The above settings apply to various elements such as fresh air, defrost, floors, center vents and temperature. In this way, passengers can control the air temperature as well as the direction of air flow.

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