Car AC Fan Speeds Up And Slows Down – Check AC system

I have noticed that the fan speed of a car’s aircon system begins to fluctuate and might cycle, speeding up and slowing down. This can be quite annoying and uncomfortable, but understanding why this happens and how to deal with it.

Why is my AC blowing hard and then soft? To address car AC fan speed fluctuations, check the blower motor for wear, clean air ducts to avoid slow airflow, and ensure proper operation of the AC system to maintain constant fan speed.

In this post, we look at some of the reasons you will find car AC fan speed fluctuations and what you can do to troubleshoot them.

Understanding AC Fan Speed Variations And Their Causes:

AC fan speed is adjusted automatically as a protective mechanism that goes hand in hand with the temperature of the evaporator coil.

If the evaporator and coils are too cold, the fan slows down to prevent freezing; if they are too hot, the fan speeds up to cool them down to ensure that the system is efficient in cooling.

This cycling is part of the system’s regular operation, and no specific remedy is needed at that point. An air conditioner fan with continuously varying speed can result from multiple causes. Lubrication of the motor shaft might solve the problem if it is related to bearing friction.

However, if motor windings are shorting out, motor replacement becomes necessary to ensure smooth and consistent movement of the fan blades. With autonomous temperature control, the sensors that notify an electronic control unit how to manage airflow can fail, resulting in too little cold air being directed to the interior.

Why Does A Car Blower Motor Or Fan Speed Up And Slow Down?

1. Low Refrigerant Levels:

Most automobile air conditioning systems need to pressurize the refrigerant, commonly known as Freon gases, to help cool the cabin. When these gases are at a low level or amount, the air pressure will first pump very fast to cool the cabin; otherwise, the cooling will be inadequate, making the fan move at slow speeds and giving off cold air in lesser amounts.

2. Compressor Or Blower Motor Issues:

Inconsistent airflow and uneven cooling may result from the failure of the compressor or blower motor, which has started failing and causes the fluctuation of fan speed.

If the compressor is not working correctly, the refrigerants will not circulate correctly; hence, they will not cool the place constantly but will show variable temperatures and changing speeds.

3. Voltage Regulator Adjustments:

The alternator produces more electricity as you crank the engine, resulting in higher battery voltage. The voltage regulator then adjusts the voltage supplied to the fan, causing the fan to turn faster. When it returns to idle and braking, check with the voltmeter where the voltage regulator lowers the voltage (up to 0.5 volts is standard); the fan slows, resulting in low air.

4. Worn-Out Fan Motor:

You may realize that the blower fan runs, but the motor has lost the ability to blow air at higher rates because the fan motor could be a problem due to motor resistors that have worn out over time. When the engine loses efficiency, it may produce a different amount of coolant, and the blower speed slows down or blows cold.

5. Blend Door Issues:

If the fan is running at higher speeds and only a tiny amount of cold air comes out of the vents, the fan motor might be functioning well, and the probable cause is the blend door.

• Actuator Failures: These parts work to open and close the blend doors, and, like any other mechanical device, these actuators may fail over time. This will result in blocked flow and temperature management issues.
• Stuck or Broken Blend Doors: The blend doors might, in turn, get stuck or break. As a result, they will fail to allow the air to be channeled correctly.
• Obstructions: Obstructions from various debris, including plastic bags, wrappers, leaves, or anything else foreign, can obstruct the airflow and result in low airflow.

6. Cabin Air Filter:

Cabin air filters can become obstructed, hindering the inflow of fresh air into the air conditioning or heating system (HVAC System) and, therefore, reducing the overall inflow and effectiveness of cooling or heating.

How to Solve the Problem of the Blower Fan Speeding Up And Slowing Down

1. Add Refrigerant:

First, diagnose the low refrigerant issue in your car’s air conditioning system. If no large leaks are spotted, carefully and securely add the correct refrigerant to the system according to the low-pressure port, as directed by the kit. Monitor the pressure, stop when it is within the required range, and test the air conditioner for better overall cooling.

2. Inspect Faulty Compressor Or Blower Motor:

This can be done by checking a faulty compressor or blower motor with a mechanic which needs replacing. Also, check the electrical connections, fuses, and relays. Ensure the motor is not clogged or dirty. Extensive repairs or replacements usually require the expertise of a specialist.

3. Engine Revving: 

The fluctuation of the fan speed caused by engine revving is a typical characteristic of the electrical system. This characteristic does not require a direct remedy as it is simply an automatic response to fan speed variations regulated by the engine’s voltage regulator.

4. Replace Worn Out Motor Fan:

Identify and access the fan motor, usually under the passenger-side dashboard. Carefully disconnect the wiring, remove the old fan motor, and replace it with a new one (OEM Fan would be best). Reconnect the wiring, rebuild any removed components or panels, and reconnect the car battery.

5. Replace Air Filter Clogs:

Inspect and change the cabin air filter regularly or every 12,000 to 15,000 miles per the manufacturer’s recommendations. This simple maintenance task can help maintain airflow and keep your car’s air conditioning system working optimally.

6. Inspect Obstructions: 

Remove panels and look for any obstructions or damage. Gently check if a door is stuck and try to unstick it. If the door is broken or the actuator has failed, check the air intake and the vents for clogs and clean out any obstructions. Clean the area surrounding the vents regularly to prevent dirt from entering the system.

Why Does My Air Conditioner Fluctuate In My Car?

Inadequate, fluctuating fan speeds may be due to a lousy circulator motor. Your expansion valve might also be failing. This critical component experiences wear and tear, leading to inconsistent operation and sporadic cooling.

An erratic electrical system, mainly caused by a malfunctioning alternator or a weak car battery, will cause erratic voltage distribution to your blower motor. The result may be spontaneous fan speed fluctuation.

The AC compressor pressurizes and cools the refrigerant, which carries the refrigerant through the entire air conditioning system to regulate the cabin temperature. Any fault in the compressor will cause AC system failure, including fan speed.

Why Does My Car AC Fan Slow Down?

A defective or worn-out circulator motor can cause low fan speed. When a component wears out, inadequate airflow is typical, resulting in low fan speed. Clogged air ducts or dirty air filters can also cause zero air movement in the AC system, reducing fan speed.

Clean and service the air filters accordingly. Failures in the electrical system, such as a bad car battery or a failed alternator, would hinder the proper power flow to the blower motor, thus affecting its performance.

The evaporator draws heat from the air, which is crucial for cooling. The air will not be cooled to the right temperatures if it malfunctions. Additionally, problems with the condenser also lead to inadequate cooling processes.

Relevant Questions:

How Do I Know If My Fan Motor Or Capacitor Could Be Better?

Some common symptoms are weird noises from the fan motors or compressor units, a time delay in start-up, no cool air even after running continuously, and flickering lights due to voltage fluctuations.

How Much Does It Cost To Replace An AC Blower Motor?

The USA spends around $550 to substitute a blower motor system, including labor costs. You may be charged just $130 in labor fees if your device has a warranty. More complex models may cost $2000 or more to install, particularly those that are difficult to reach.

Will AC Work If The Blower Motor Is Bad?

An air conditioner needs a blower motor to work and perform its function. If the motor does not function as required, it can affect the comfort and air quality inside your vehicle.

Can You Drive A Car Without The AC Blower Motor?

Is it possible to drive without an AC blower motor? Yes, however this is not advisable. More than just the air conditioning depends on the blower motor. When it fails, there is a risk of overheating the engine.

Why My Car Ac Fan Changes Speed While Driving?

Different factors such as fluctuations in the electrical system, a faulty blower motor resistor, or climate control unit issues may cause your car AC fan to change speeds. It is recommended to inspect these parts regularly for proper functioning of the fan.

Ac Fan Speed Fluctuates Only On Blower Level 3?

Only 3rd speed BL3 If you will find blower level 3 vary speed then it is possible that there could be a problem specifically affecting that setting with the blower motor resistor. To stabilize the fan speed, replace or inspect the resistor.

Why Is My Ac Slowing Down And Speeding Up?

If the power supply fluctuates, the air conditioning will become slower or faster. This could also be due to faulty thermostat signals or blocked filters that limit airflow. To check these components comprehensively, either carry out self-checks or consult experts who are well versed in such issues.

Why Is My Fan Speed Fluctuating?

There could be several causes for each change in the speed of the fan of the air conditioner in the car. Thus, people should know about common problems with this device and determine why they happen—a broken blower motor, voltage supply troubles or faulty operation of an air conditioning compressor. That is why one should eliminate all malfunctions at once not to spoil the drive.

Blower Fan Slows Down When I Stop Or Slow Down At Red Light?

If the current changes in voltage happen to your AC, it may slow down or speed up. The problem could also be due to a faulty thermostat or dirty filters that reduce airflow. You should check these components thoroughly either by yourself or with the help of a professional who is familiar with such issues in order to diagnose it properly.

Ac Blower Speed Slows Down On Its Own When Set To High And Running Car For A While?

Consider a situation where an AC blower becomes slower after running for some time on its highest setting; this might mean that it has been overheating and experiencing voltage drops. Examine the blower motor, resistor and electrical connections which could affect their performance.

Finalization:

Every time your car’s AC fan speed fluctuates, there could be many reasons behind it. Hence one must know these common issues and be able to determine what is causing them to be fixed—a bad blower motor; voltage supply problems; or even trouble with the AC compressor. Therefore any malfunctions should be repaired at once so that they do not interfere with performance while on trips.