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How to Test Blend Door Actuator: Car Programming Hacks

A blend door actuator is a very useful device that helps to control airflow and temperature in your car. If you want to know how to test blend door actuator, here we have provided a complete guide.

This art is a small-sized electric motor that features a sensor that is connected to the vehicle’s climate control system.

When you adjust the car’s temperature down and up or its intensity, then the signal goes through the actuator. The blend doors actuator is a very small-sized plastic box.

Automation has been established in the car; it is now possible to control different variables through the electronic system.

Such is the case of fuel supply, which has evolved from mechanical operation (carburetor) to electronic fuel injection systems.

This time we are going to talk about electronic engine management. To begin, we start with the concept of sensor and actuator.

Then we identify the different sensors that are part of the injection system.

Sensors vary depending on the injection system, some may be present in all systems, and some may not. Let us find out more about blend door actuators:

How to Test Blend Door Actuator: Quite a Simple Method

If you have come this far, you can already imagine that the most frequent AC failures in your car are going to be determined by

  • Failures in the refrigerant gas,
  • Failures in the compression system,
  • Electrical failures, or
  • Failures in the air circulation system.

One of the main problems with your car’s cooling system is that the air conditioning is used only seasonally. This means between two and five months a year on average, depending on the area.

Being between 9 and 7 months without being used can cause deterioration in the system due to its lack of use.

It is advisable that during the autumn, winter, and spring, you turn it on with some regularity to prevent possible damage to the system and detect them in time.

Let us find out how to test the blend door actuator?

Why Blend Door Actuator Isn’t Working?

The more sophisticated the system, the more elements, and components can intervene in its malfunction.

In the most advanced systems, everything works from the control of an electronic switchboard.

It is the one in charge of establishing the magic formula to give you the climate you have selected. But we are going to focus on the most common causes of the base elements of a system.

  • Refrigerant-related Faults

Refrigerant gas, typically R-134a, can be lost but is not consumed. The system establishes a circle by which the gas is recovered in its entirety, in its gaseous state, and is reused.

It also does not have an expiration date. This means that when there is a problem of lack of refrigerant gas, recharging it is not enough.

The leak must be detected and repaired. That is why you should not make the mistake of going to the lure of “we recharge your air by”.

Most likely, you have recharged so cheaply that it lasts, at most, a week. The leak can be in the gas tank, less frequently, or in the ductwork.

The vibrations of the engine make the gas have to be guided by flexible hoses.

This is a porous material to which the conditions of heat and lack of humidity due to its disuse for months can alter its properties. It dries out, hardens, and pores open or mismatch the fittings.

It is necessary to check the circuit and detect where the leak occurs. Dyes are generally used for this. But for you to detect if your air circuit is losing gas, one of the simplest ways to do it is by smell.

If the air you introduce into the vehicle has a strange odor, you should take it to the workshop and have the circuit checked.

Only once the leak has been detected and repaired should you recharge the circuit.

But understand that, as a principle, the gas pressure in the air circuit should always be that of the original charge. If this decreases, there will be a leak.

  • Compressor Fault

It is the basic mechanical part and it can break down. In this case, the circuit stops working.

You will notice it because, generally, you will have perceived some type of noise from the vents. The failure may affect the compressor itself or some of its valves.

  • Electrical Failure

One of the easiest and cheapest ways to repair an air conditioning fault in your car is to check the fuse that controls it. If this is melted, you can change it for less than one dollar.

The electrical failure does not affect the compressor. This is powered by the car’s engine. But it does affect the fans that blow air through the circuit.

  • The Cabin Air Filter

These filters have the mission of cleaning the air of impurities. This can mean that over time, these impurities that it collects become enough to completely or partially plug the filter.

Cleaning it is the best solution, and its replacement is usually essential in these cases. But it is worth it. You will have air conditioning again without great economic disruption.

There is something picaresque with the air conditioning services. They tend to snag cheap recharge deals in a few minutes, taking advantage of the impending need for heat.

Now you know that if you need to recharge, it is because you need to repair and you must take it to a serious site that offers you just that. First, detect the leak and then, now, recharge.

Required Tools During the Process

If you want to test blend door actuator at home DIY, it is important to have tools for this project before you begin. Thus, you will save your frustration and also your precious time.

List of the tools required during this project:

  • Socket
  • Ratchet set
  • Toolset
  • Small-sized screwdriver

If you are turning your car ON and if you will notice that you are not able to get heat, you should recalibrate the heater, or you simply need to change the blend door actuator.

If you are not sure or if you do not have these tools, it is advisable to take your car to the nearest mechanic or service center and get it checked.

Blend Door Actuator: What & Why?

The objective of the sensor is to know the temperature of the engine; it does so from the temperature of the coolant, sending a signal to the ECU to regulate the mixture and the ignition time of the fuel.

  • Air Temperature Sensor (IAT-Intake Air Temperature)

As its name says, it measures the temperature of the air. With this signal, the ECU can adjust the mixture with greater precision, although this sensor does not affect the mixture, its malfunction leads to engine failures.

  • Airflow Sensor (MAF-Mass Air Flow)

It is located between the air filter and the butterfly. The function of this sensor is to measure the current of sucked air that enters the motor.

Its operation is based on a resistance known as a hot wire, which receives a constant voltage, reaching a temperature of approximately 200° C with the motor functioning.

Using the information that this sensor and other factors such as air humidity can determine the amount of air.

  • IAC Valve (Idle Air Control)

The IAC sensor or IAC Valve plays an important role in regulating the engine revolutions at idle by regulating and managing the intake of air in the ignition chambers.

In conclusion, the main function of the electronic engine management system is to regulate fuel consumption and control polluting emissions.

To achieve this, it uses the sensors and actuators that we develop in the article.

Cautions During the Process

All cars have multiple security systems, and it is important to know them, know how to use them. And not despise their usefulness since the life of the vehicle’s occupants depends on them.

While testing blend door actuator by yourself, it is important to note down these cautions during the process:

  • Make sure there are no cables or loose parts inside the engine compartment.
  • Disconnect the electrical system before starting work.
  • Keep the work area clean, orderly, and ventilated.
  • Use specific equipment to handle and move heavy components.
  • Secure the motor anchor points on the test bench.
  • Check the levels of the different fluids before starting the engine after the repair.
  • Have a fire extinguisher handy and be aware of the existence of flammable materials in the work area, keeping any combustible element or solvent away from heat.
  • Check before starting the repair what previous maintenance the vehicle has received.
  • Identify whether the battery needs to be disconnected, to minimize the risks of handling elements subjected to high voltage. 
  • If it is necessary to disconnect it, it is important to ensure that all electrical components in the vehicle are switched off, as well as to disconnect the ignition system and store the key.

Blend Door Actuator Failure Symptoms

The engine coolant temperature sensor (the “water” of the engine, to understand us) has several functions, all of them very important:

  • Used to adjust the amount of fuel to be injected.
  • Used to connect the electric radiator fans.

In the first case, if the engine is cold, an additional amount of gasoline must be injected to counteract the condensation losses in the intake manifold and to warm up the engine earlier.

In the second case, how to test blend door actuator if the sensor detects that the temperature exceeds a certain limit, the system will send the radiator fan the order to operate.

So that the airflow increases and thus avoid a disaster that will screw up our lives and our pockets.

The coolant temperature sensor is normally located near the cylinder head coolant outlet as this is usually the point where the liquid is hottest.

Symptoms of a Bad Coolant Temperature Sensor

Since this is a coolant temperature sensor, one critical to the integrity of the engine, if it fails, you have to have a plan B so that the engine does not blow all the way.

If the sensor signal fails, the ECU will calculate a certain temperature value.

Symptoms of a faulty temperature sensor can be:

  • Increased gasoline consumption (ECU may tend to enrich the mixture)
  • Black smoke in exhaust gases (rich mixture)
  • Engine overheating (the electric fan may not blow up in time or may never jump directly)

Let us find out some of the common symptoms of a bad blend door actuator:

Noise: If you notice any squeaking or repetitive droning sound from the dashboard, it is one of the signs of a faulty blend door actuator.

Specially, you will notice such sounds when you are ON the car’s air conditioner.

Knocking: It is one of the unusual symptoms. If you are experiencing such a knocking sound, it will be surely an issue with the blender actuator.

At the time, when you start your vehicle or only your AC system and if you will listen to any sound such as tape on the door, it is also one of the signs.

Inconsistent Airflow: If your blend door moves forth and back, then the car’s airflow diverts or maintains incorrectly.

That is the pretty standard sign that there is surely an issue with

Where is the Blend Door Actuator Located?

If your car has electric locks, surely you have wondered how does that peculiar comfort accessory works, which prevents you from stretching your arm to each door to be able to open it for your passengers?

This mechanism is currently found in most vehicles, usually in equipped versions.

However, to operate thousands of times in the lifetime of an automotive, its system has been perfected and is now very reliable.

For its part, the way to open or close these locks varies from one car to another.

It can be by pulling the knob on the inside of the door, through a button on the center panel or doors, with remote control, and through a combination lock while outside the unit.

Inside the doors, there is a device that does all the “magic” of opening and closing; it is known as an actuator.

It is located below the lock hooked to it using a rod; at the same time, another rod connects the bolt with the opening handle.

In addition to the above, the actuator is connected to the power outlet to function. Although it sounds obvious, as the actuator moves the latch-up, the door handle engages in opening the door.

When the actuator moves the bolt downwards, the opening mechanism is disconnected. This device works in a very simple way.

A small electric motor with rotary movement transmits this oscillation to a series of gears, which are connected to a rack that transforms said movement into a linear one that moves up and down to drive the bolt.

There are different types of actuators. However, the operation of each one is very similar.


We are sure now you have learned the entire process of how to test blend door actuator? It is advisable to keep testing the door actuator as it is one of the important parts.

It is an electromechanical mechanism whose function is to provide a movement or act on another mechanical element.

However, the movement or force generated by the actuator can be Pneumatic pressure, hydraulic pressure, and electric motive force.

Depending on its source, it can be called in the same way: pneumatic, hydraulic or electric.

It is a device that gives the fluid or fuels the energy necessary to move through the carburetor or injector and then enter the intake valve, where it later passes to the cylinder.

The injector is the element in charge of spraying the gasoline from the pressure line inside the intake duct.

It is a solenoid valve capable of opening and closing many millions of times without fuel escaping and reacts very quickly to the electrical pulse that operates it.

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