What causes a fan to speed up and slow down?

Author: Sheldon Steuber  |  Last update: Saturday, April 12, 2025

The most common cause is a dirty or clogged filter. This can cause the fan to struggle to draw in air, resulting in the fan speed fluctuating. Another possible cause is a faulty fan motor or capacitor, which can cause the fan to run at different speeds.

Why does my fan keep going fast then slow?

Poor capacitor

A fan capacitor provides the appropriate power to the fan. 90% of speed issues in fans are caused due to poor capacitor performance.

How to know if a fan capacitor is bad?

The usual symptom is the fan motor just hums without rotating or the motor overheats on one or more speed settings. When these capacitors fail, they often develop a noticeable bulge or discolored region in the thin plastic outer casing of the capacitor.

Why is my ceiling fan speeding up and slowing down?

Dust and dirt build-up on fan blades can quickly impact the performance high-speed ceiling fans, causing them to run slower and reducing their airflow. Ceiling fan blades gather dust over time; this dust adds extra weight and creates an uneven resistance.

How do I fix slow fan speed?

Steps to Make Your Fan Move Faster
  1. Clean and balance the fan blades. To clean the ceiling fan, slide one fan blade into the pillowcase and wipe the top and bottom of it. ...
  2. Lubricate the fan. ...
  3. Replace the capacitor. ...
  4. Replace the speed controllers.

How to fix a slow fan

Why is my fan speed not constant?

If a ceiling fan runs at high speed during off-peak hours and at low speed during peak hours, then it is sure that speed change is due to voltage fluctuation. To counter this problem, you can replace the old capacitor with a new one. If the problem still persists, try to replace both the bearing of the fan.

Why is my standing fan not spinning fast?

If there is sticking or too much resistance, you may just need to lubricate the fan shaft. Over time, the lubricant on the standing fan shaft will wear out as the standing fan blades turn. Re-oiling the fan shaft usually solves the problem. Dry, sticky fan shafts are the most common cause of blades not spinning.

What affects the speed of a ceiling fan?

The higher the CFM of a fan, the more air it can move, and the faster it will spin. Ceiling fans with higher CFM ratings are better suited for larger rooms or areas with high ceilings. 2. The number of blades and sizes: The number and size of blades on a ceiling fan can significantly affect its speed.

Why is fan speed slow in summer?

In summer due to high temperature of the environment , resistance of the winding of a fan increases, compare to low temperature in winter. Due to higher winding resistance current will decrease and fan rotates slower in summer compare to in winter .

What are the 2 typical signs that a capacitor is bad or has failed?

The short answer is you may have a failing AC capacitor if you are experiencing any of the following symptoms:
  • Your AC system isn't blowing cold air.
  • You hear a humming noise coming from the outdoor unit.
  • Your monthly energy bills are rising unexpectedly.
  • Your air conditioner will shut off unexpectedly.

How much does it cost to replace a ceiling fan capacitor?

The average cost for repairing a fan motor is between $80 and $350, including labor and materials. The problem may require the replacement of the capacitor for $90 to $300, the ball bearing for $80 to $175, or the motor for $100 to $350.

Can a bad capacitor ruin a fan motor?

If your HVAC capacitor is bad, the motor will run at higher amplification, run backwards or stop running altogether.

What causes standing fan to slow down?

After some good amount of time, it is possible that an electric fan would run a little slower than when it was first used to. This may be caused by the following: fan being dusty, friction, and damage to the bearing. Dismantle the electric fan and rotate the propeller with the use of your hand to see if it is stuck.

Why do fans get weaker over time?

1> Dust and Debris: Over time, dust and debris can accumulate on the fan blades or within the motor housing, causing friction and reducing the efficiency of the fan. This buildup can slow down the fan's startup time. 2> Lubrication: The fan motor may require lubrication to operate smoothly.

Why does my fan speed go up and down?

There are a few possible causes for this issue. The most common cause is a dirty or clogged filter. This can cause the fan to struggle to draw in air, resulting in the fan speed fluctuating. Another possible cause is a faulty fan motor or capacitor, which can cause the fan to run at different speeds.

Why are my fans fluctuating?

Fan speed fluctuations are normal. If there would be some physical balance issues with blades or unusual noises, those would be issue. Same goes to other things too.

Why does my fan keep surging?

Scan your computer for malware

Malware (virus, spyware, trojans, and so on) can cause a computer fan to run constantly due to an overload on the processor (CPU), this in turn causes the fans to run constantly and fast. Spyware and other types of malware are a big cause of many computer problems.

How to fix a slow fan?

Implementing Cleaning and Lubrication

Dust and dirt buildup can cause your fan to slow down and wobble. Cleaning the blades, motor housing, and other parts of the fan can help reduce noise and improve its efficiency.

Why do fans become slow?

A ceiling fan's speed can slow down due to capacitor failure, voltage instability, imbalance in blades, wear and tear of bearings or lack of lubrication.

What determines fan speed?

By just the basic rotational dynamics, the speed of a fan will depend on the moment of inertia of the fan. This means if you have a fan with heavy blades, it should run much slower than a fan with lighter blades (assuming motor speed and size of the blades are the same).

What is the common problem of an electric fan?

Whether the blades aren't spinning or the fan is making tons of noise, most issues with an electric fan are caused by poor lubrication or blockages in the vents. To solve most problems with an electric fan, disassemble the fan, lubricate the central pin and bearings, and clean out the vent and motor case.

How can I make my fan more powerful?

Dust and debris accumulation on fan blades can impede airflow and reduce efficiency. How to make a fan work better? Regularly clean your fan blades using a damp cloth or a vacuum cleaner with a brush attachment to remove dirt and dust. This will help your fan work more efficiently.

How to clean a fan motor?

Clean the Fan Motor

The ceiling fan motor's cover should keep most dust out, but some may still get in. To clean the motor, simply apply a vacuum to the slits on the top of the motor cover. This should help remove the excess dust from your fan's motor.

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