4 Signs Of A Bad Or Failing Blend Door Actuator

Blend Door Actuator

Properly functioning A/C and heat is critical to an enjoyable ride in your car. If the climate control system starts to act up or isn’t providing the temperature you need, you will dread getting into the car.

One problem you could be dealing with is a bad blend door actuator. What are the symptoms of a bad blend door actuator, so you can recognize the issue?

In this guide, I evaluate the top symptoms that something is wrong with the bad blend door actuator. I also look at its location, function, and the average replacement cost. At the end of the article, I discuss how to test the blend door actuator and explain some of the reasons this vital part can fail. 

Symptoms Of A Bad Blend Door Actuator

The most common symptoms of a bad blend door actuator are problems with your car’s air conditioning controls and strange noises coming from the air vents. You may notice inconsistent temperature or airflow.

Here is a more detailed list of the most common signs of a bad blend door actuator to look for:

1. Strange Sounds

noise from car

As the blend door actuator fails, you could hear a variety of noises. When first starting the climate control system, you may hear knocking noises. There could also be a clicking sound coming from the dashboard area. These sounds could be faint or loud, and they can be repetitive or constant. It’s even possible to deal with intermittent noises, making it even more difficult to diagnose. 

While knocking or clicking seem to be the most prevalent noises, they aren’t the only ones that are noticed. There could be squeaking or droning noises as well. As the problem gets worse, you might notice the sound getting louder, which is one reason it’s helpful to have it checked out at the first sign of problems.

2. Inconsistent Temperature

ac blowing air

As you turn on the air conditioning or heat in your car, you expect to feel a certain temperature coming out of the vents. If you get anything different than that, you know there’s a problem. What’s even more alarming is when the temperature changes by itself.

If you are noticing a mixture of heat and cold at various times, it’s a strong indication that something could be wrong with the blend door actuator. While the controls themselves won’t change, the temperature will make dramatic adjustments. 

RELATED: Car Heater is Blowing Cold Air? (7 Causes & How To Fix it)

3. Wrong Temperature

car air climate controls

Once the blend door actuator breaks completely, the wrong temperature could come out of the vents full-time. This could be present through heat coming out with the air conditioning on and vice versa. 

If you’ve just changed the controls from one to another, it’s okay to wait a minute and give the system time to adjust. Beyond that minute, the temperature should reflect the controls or you might need to get a new blend door actuator installed. 

RELATED: Car AC Not Blowing Cold Air? Common Causes (& How to Fix)

4. Inconsistent Airflow

When the blend door actuator is working as it should, air will flow out at a good rate. It should remain consistent at all times. If you get harder airflow at some times than at others, there’s something wrong. Airflow is interrupted when the blend door moves back and forth, which diverts the regular flow and creates inconsistencies. 

Inconsistent airflow alone isn’t enough to prove there’s a problem with the blend door actuator. This problem can also be caused by a failing fan, a clogged cabin air filter, or a blocked intake. 

RELATED: 3 Signs of a Bad Blower Motor Resistor (& Replacement Cost)

Blend Door Actuator Function

To grasp how the blend door actuator works, you need to understand the climate control system in general. The purpose of this system is to manage the control of airflow and temperature into the car’s cabin. There are multiple parts making up the system, including a blower motor, heater core, evaporator core, various vents, ducts and doors. 

There are three types of doors that operate most automotive climate control systems. You have the inlet door, a mode door, plus the blend door. The job of the inlet door is to determine whether the air moving through the cabin comes from outside, where it’s fresh, or if it’s going to be recirculated. Mode door controls are meant to determine where the air discharges, whether you want it through the vents or on the floor. 

The blend door goes by several other names. It can be called the mixture or temperature door. Either way, it’s needed to manage the temperature coming from the system. The blend door determines whether the air comes from the evaporator or heater core. 

Most climate control systems rely on an electric motor as the actuator. This actuator is needed to control what position the blend door sits at. However, older vehicles used a mechanical cable, which doesn’t seem to suffer from the same problems. 

As you change the temperature on the climate control system, power gets sent to the blend door actuator. This power forces the device to control the door and move it in the appropriate direction based on the settings. The blend door actuator can also contain a sensor that is always monitoring the position of the door. 

Where is the Blend Door Actuator Located?

The blend door actuator can be located in numerous locations. However, most are found behind the dashboard, near the blower fan. You may be able to get to it by removing the controls or by going underneath the dashboard. 

If the air conditioning system can only be controlled in one place for the entire vehicle, there should be one actuator. However, if you are using a dual- or tri-zone climate control system, there should be multiple actuators and blend doors to control each zone. 

If you want to find the location of the blend door or multiple doors, it’s best to reference a service manual. If you don’t have that, you should find the information online. 

Blend Door Actuator Replacement Cost

On average, it might cost $150 to $550 to have a professional mechanic replace the blend door actuator. The cost of the blend door actuator itself isn’t normally expensive, but it’s not the easiest part to replace in many cars.

Additionally, you will pay extra if you want OEM parts instead of an aftermarket component or if you have a luxury car that requires a specially-trained technician.

If you want to save money, you don’t need a lot of tools to replace the blend door actuator at home. However, it can be well-hidden behind the dashboard, requiring you to remove a bunch of parts to access it. 

RELATED: How to Reset a Blend Door Actuator

How to Test a Blend Door Actuator

If you want to figure out whether the blend door actuator is causing the climate control issues, you can follow a simple set of instructions to test it.

However, the methods for testing it varies based on what type of vehicle you drive, so it’s important to read the service manual. Aside from what you read in the manual, here are a few tips that might help you.

  1. Try applying power directly to the blend door actuator. If the power moves the door actuator, the problem could be a feedback sensor instead. It’s also possible that the output signal is causing the issues. For this, you need a correct wiring diagram to not damage the actuator or car’s electrical system.
  2. If you have a high-end scan tool, you can check for diagnostic trouble codes that are related to the blend door actuators. These codes won’t be read by cheap OBDII code scanners.
  3. You can also use a high-end scan tool to test the blend door actuator. Send power to the door to see how it responds. 

If you don’t have the tools necessary to perform diagnostics, it’s best to get help from a professional. Otherwise, you could start replacing parts that aren’t bad, thereby wasting your money. 

RELATED: 10 Best Automotive Scan Tools for Car Diagnostics

Why Does the Blend Door Actuator Fail?

As with any car part, the blend door actuator can fail simply because of wear and tear. It’s possible that the motor has worn out over time, especially if it has been used heavily. If you live somewhere with extreme temperatures, the actuator could fail prematurely.

Additionally, there are many electrical circuits that are part of the air conditioning and heating system. If any of these circuits fail, the blend door actuator could malfunction. There’s also the possibility that some of the problems are caused by a blown fuse, so don’t forget to check those too.

What is a Blend Door Actuator?

The blend door actuator is a component of your car’s heating and air conditioning system. It is responsible for opening and closing the blend door that allows hot or cold air to mix with the incoming airflow in order to maintain the desired interior temperature.

What is the difference between a blend door and a blend door actuator?

The blend door is the flap that controls from which direction the climate control system should take the air. The blend door actuator is an electronic component that controls this blend door flap. The climate control panel or control module controls the actuator.

What happens if you don’t replace the blend door actuator?

If you don’t replace the blend door actuator, nothing will happen except that you won’t be able to control the temperature coming from your car’s vents electronically. But if you’re fine with the temperature, you most likely won’t notice other problems.

How do you test a blend door actuator?

The best way to test a blend door actuator is to use a diagnostic tool compatible with your vehicle. This should allow you to send a desired signal to the actuator, which you can then confirm with a multimeter or by visually inspecting it.

The blend door actuator is hidden under the dashboard and is a part that you will never think about until it goes bad and you will notice temperature problems from your climate system. Fortunately, this small part is easy to diagnose, but in most cases quite difficult to replace.

I hope you enjoyed this article and now know everything you need to know about the blend door actuator, and can now make the decision whether you need to replace yours or not.

Categories: Air condition

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