Blend Door Actuator Symptoms: How to Test and Replace ?

Blend door actuator is an HVAC system component that controls the temperature and airflow inside a vehicle. Whenever you have a problem controlling the air circulating inside your vehicle, or if it’s stuck at blowing full blast, or making a tapping noise as if someone is tapping on your door, chances are you have a problem with the blend door actuator. Knowing defective blend door actuator symptoms will help you do a quick blend door actuator repair and save you from expensive repair costs.

What is the blend door actuator?

A blend door actuator is an electric HVAC motor that works together in harmony with sensors connected to your climate control system. When you adjust the actuator airflow intensity or turn the temperature dial-up and down, the input signal passes through the actuator. What does the actuator do? The blend door actuator decides whether the air is going to come through the mid-vent, floor vents, and control defrost, and so on.

Some cars have a dual blend door actuator that enables the driver to control the climate in different time zones. The dual blend door actuator is mostly found on newer cars with the feature to set front or rear passenger climate separately. The blend door is a plastic box located on an under-trim panel, responsible for sending cool or warm air within the vehicle to keep the passengers comfortable.

You might need warm air when the vehicle is cold or vice versa; when you turn the climate control dial, the blend door will have to send in the desired air. If you need cool air, the actuator will turn to the close position to prevent heat from entering the vehicle.

blend door actuator reset

Blend door actuator symptoms

Whenever any system component of your vehicle fails, symptoms will pop up to tell the driver of an issue that needs attention, and the blend door actuator is no exception. If you’re searching for any vehicle or Tacoma blend door actuator symptoms, you will find the answers in the next few paragraphs.

Clicking sound beneath the dashboard: If you’re having problems with your climate control, turn on the AC and climate control system and pay close attention to the dashboard. Suppose you hear a droning or faint clicking repetitively from the dashboard, around the center area, where your HVAC system control knobs are located. In that case, that indicates you have a bad blend door actuator. A faint clicking or droning sound underneath the dash is usually a blend door actuator noise.

This noise may be obvious when you switch on your vehicle AC system or turn on the climate control dial. Most times, switching the climate control dial can temporarily stop the noise. You will hear this sound due to a bad door blender in some cases. If the actuator plastic gears deteriorate, the teeth will break off and cause slipping when you turn the HVAC knobs.

Knocking sound under the dash: This is quite uncommon, but whenever you notice a Knocking sound under the glove box, the blend door actuator is likely the culprit. Each time you notice a Knocking or tapping sound when you start your vehicle or turn on the HVAC system, it signifies an issue with the blend door actuator.

Inconsistent temperature: An Oscillatory moment of your blend door will cause the airflow to be diverted incorrectly. And that’s a good indication you have a bad blend door actuator.

Wrong Temperature: Bad blend door actuators are mostly the cause of malfunctioning climate control systems. Suppose your airflow doesn’t heat up to the operating temperature or AC blowing hot air instead of warm air. In that case, you should inspect or contact your mechanic for proper inspection and blend door actuator replacement. If you have a damaged blend door actuator, it’s either the plastic gears have worn out or the actuator has failed. If any of these happens, you won’t be able to control your vehicle climate.

How do I test the blend door actuator?

If you notice any of the symptoms above, inconsistent temperature, Knocking sound under the dashboard, clicking sound under the dashboard, or the wrong temperature, you have to test or contact your mechanic for a blend door actuator reset. Most blend door actuators diver the temperature and airflow inside the vehicle by opening and closing the heater flap located at the back of your glove box.

To test the blend door actuator, disconnect your vehicle’s negative terminals. If your vehicle has radio code, ensure you write it down, or better still, you might perform a calibration. You might decide to take your vehicle to a mechanic garage if you don’t have a calibration machine. If the heater is blowing cool air, the problem might be you have a bum blend door motor.

When you observe the symptoms above, you should inspect the heater hoses, if the heater hoses are hot, it’s a clear indication, and you should fix the problem as soon as possible. The next thing is to find the actuator; it’s usually located underneath the glove box on or beside the heater box. You will need an assistant to help you switch the climate temp in various modes while watching out for the movement. If the blend door actuator doesn’t move as you switch the climate temp in different modes, you have a bad actuator that needs replacement.

You have to also check your blend door and the linkage. They can also cause the same issues if they are bad. If this is the case, you will need professional assistance. Watch this video for visual clarification.

How to replace a blend door actuator

You can save blend door actuator replacement costs by following this easy and straightforward guide. You will only need to pay for the part cost. You will need common mechanic tools like screwdrivers and a 5.5 mm socket set, depending on your vehicle model.

Remove the glove box or lower dashboard cover: Remove the glove box on the passenger side dash with a screwdriver or small socket set and ratchet handle. The glove box mounting bolts are usually in hidden areas, locate and remove them out of the way. Once you have removed all the fastening screws, gently remove the glove box or the underneath dash panel.

Remove the blend door actuator: The actuator is placed on or beside the heater box. Remove the wiring clips with a screwdriver. You need to be gentle; these clips can be brittle and break. After removing the clips, press the tab on the wiring connector and pull it off. Inspect the connector for corrosion and rust as it could cause resistance. Clean the connector with an electrical cleaner if need be. Next, remove the mounting screws from the actuator. These are usually two or three screws. You might need a small universal socket to remove some screws in a hidden place. The actuator should fall off, or you need to gently wiggle it off.

Turn the air door pivot: Before mounting the new blend door actuator, you have to manually turn the blend door to make sure the blend door is not stuck, which could damage the new unit. Grab the blend door and turn it in both directions. It should turn freely to both sides; if it’s hard to turn in full position, there could be an obstruction that could cause the new blend door actuator to fail. If the blend door isn’t moving freely, you have to remove the heater plenum and fix it before mounting the new actuator. To confirm that you’re replacing the right blend door actuator and to test door operation, turn the blower and work the blend door in both directions. You should feel a temperature from the dashboard air vent.

Compare and install the new actuator: Place both actuators close and compare them. Check if the wiring harness is the same. This is necessary, especially if the new actuator is aftermarket parts. If both actuators are the same, proceed with the reinstallation. Mount the actuator and insert the mounting screws by hand. Gently thread the screws with a screwdriver or socket set, and do not overtighten it because the screws are going into a plastic thread. Once you torque down the actuator, socket the wiring connector.

Reinstall the Glovebox: After reinstalling the blend door actuator, give yourself a sense of doubt and cross-check your work. Go ahead and place the cover or glove box in place. Thread in all the screws by hand. Do not tighten the first screw until you have screwed in the rest by hand because it can make the remaining screws hard to install. After successful installation, start the vehicle, switch the climate control knobs in different zones, and see if your effort has finally paid off. Watch this YouTube video for visual clarification.

Final word

Knowing what a blend door actuator is, its functions, symptoms and fixing them on time will save you from discomfort driving. In summary, the article has clearly outlined blend door actuator symptoms, how to test and replace them. In any case, if you’re not confident enough to carry out.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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