Car Ac Blows Fast Then Slow

Car AC Blows Fast Then Slow: Fix the Speed Fluctuation Now!

The car’s AC can blow fast then slow due to various reasons, with one common cause being the need for a recharge of refrigerant (Freon). Another possible cause is a dirty or dry fan hub, which can slow down the spinning of the blades.

Additionally, a failing expansion valve or a clogged air filter can also result in fluctuating air flow. It is important to address these issues to ensure optimal performance of the car’s AC system.

Why Does Car Ac Fan Speed Fluctuate?

A car’s air conditioning (AC) fan speed may fluctuate due to several possible causes. One possible cause is dirty blades and hub. When the blades and hub become dirty, they can become heavier and slower to spin up, resulting in fluctuating fan speed. However, it’s important to note that most fan hubs are designed to run without lubrication, so lubricating them may not be necessary.

Another possible cause is restricted or unrestricted refrigerant flow. If the refrigerant flow is restricted or too unrestricted, it can cause the AC fan speed to vary. This can be due to a blocked expansion valve, which removes pressure from the liquid refrigerant to allow expansion from a liquid to vapor state in the evaporator.

Clogged air filters and frozen evaporator coils can also cause AC fan speed fluctuation. Excess moisture in the evaporator core can lead to the buildup of mold and debris, blocking airflow to the cabin. Additionally, if the AC system has an open or damaged seal, it can result in a loss of air pressure to the blower.

Lastly, a tired car battery or old wiring can contribute to AC fan speed fluctuations. In older cars or cars with tired batteries, the fan speed may fluctuate as the engine is revved. This can be attributed to the decrease in power supply to the AC system.

How To Identify Ac Fan Speed Fluctuation?

Car AC fan speed fluctuations can be a frustrating issue to deal with. There are several symptoms that can help you identify this problem:

  • Hot and cold air flip-flopping: If your AC is blowing hot and cold air alternately, it could indicate fan speed fluctuation.
  • Weak airflow and sudden decrease in air pressure: If you notice that the airflow from your AC vents is weak and suddenly decreases, it could be a sign of fan speed fluctuation.
  • Momentary slowdown of fan speed: If you observe that the fan speed of your AC slows down momentarily before returning to normal, it could indicate fluctuations in the fan speed.
These symptoms can be caused by various factors such as dirty blades, a dirty or dry hub, or a failing expansion valve. It’s important to have a professional diagnose the issue to determine the exact cause and provide appropriate solutions. Regular maintenance and cleaning of your AC system can help prevent fan speed fluctuations and ensure optimal performance.

Troubleshooting And Fixing Ac Fan Speed Fluctuation

When your car AC blows fast then slow, it can be frustrating and uncomfortable. However, there are several steps you can take to troubleshoot and fix this issue:

  • Clean the dirty blades and hub: Dirty blades can become heavier and slower to spin up, causing fluctuation in fan speed. If applicable, clean and lubricate the fan hub.
  • Maintain unrestricted refrigerant flow: It is important to ensure that there are no restrictions in the refrigerant flow. Regular maintenance can help prevent this issue.
  • Clean or replace clogged air filter: A clogged air filter can disrupt airflow and affect the fan speed. Regularly clean or replace the air filter to maintain optimal performance.
  • Deal with frozen evaporator coils: Frozen evaporator coils can restrict airflow and cause fan speed fluctuations. Address this issue promptly to prevent further problems.
  • Check and replace tired car battery or worn-out wiring: An older car with tired wiring or a weak battery can cause fan speed to fluctuate. Checking and replacing these components can help resolve the issue.

By following these steps, you can troubleshoot and fix the problem of your car AC blowing fast then slow, ensuring a comfortable driving experience.

Car AC Blows Fast Then Slow: Fix the Speed Fluctuation Now!


Frequently Asked Questions On Car Ac Blows Fast Then Slow

Why Does My Ac Fan Speed Up And Slow Down?

The AC fan speed can fluctuate due to dirty blades that are heavier and slower to spin up. The fan hub might also be dirty and/or dry, necessitating cleaning and/or lubrication. However, lubricating fan hubs designed to run without lubrication is not recommended.

Why Does My Ac Fluctuate In My Car?

Your AC in the car may fluctuate due to a failing expansion valve or restricted refrigerant flow. It could also be caused by a clogged air filter or frozen evaporator coils. Additionally, a tired car battery or worn-out wiring can cause the fan speed to fluctuate.

Recharging the AC with Freon or cleaning the cabin air filter may help resolve the issue.

Why Is My Car Ac Suddenly Blowing Weak?

Excess moisture and mold in the evaporator core can block airflow and cause weak air pressure from the car AC. Another possible reason is an open or damaged seal in the A/C system. It is important to address these issues for optimal air conditioning performance.

Why Is My Ac Blowing Hard And Then Soft?

There could be several reasons why your AC blows hard and then soft. One possible cause is a dirty air filter, which can restrict airflow. Another possibility is frozen evaporator coils. It’s also worth checking if your AC needs to be recharged with Freon.

Lastly, a worn-out blower fan or motor could be causing the fluctuation in airflow.


If your car’s AC blows fast then slow, there could be a few possible reasons behind it. One common cause is that the AC needs to be recharged with Freon. Additionally, dirty blades or a dirty and dry hub can slow down the fan speed.

Another possibility is a failing expansion valve or a clogged air filter. It’s important to address these issues to ensure optimal performance of your car’s AC system.

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