Air Compressor Motor Troubleshooting – 3 Ways to Fix

Picture Shows a Motor on a Compressor
Credit: Flickr (Air Compressor Motor)

Problem in the motor is the most common and annoying problem that every compressor user faces. When the motor malfunctions, it causes a lot of trouble. For example, the lights become dim, or the compressor just hums

To solve these problems, I have created this air compressor motor troubleshooting guide. I hope this will help you resolve the problems easily.

Identification: Problems Caused Due to Motor Failure

Fuse or Breaker Blows

When the motor of your compressor doesn’t get sufficient power it overheats.  The overheated motor causes the fuse or breaker to blow.

If you use an extended chord to power up the compressor, or if you use a power bar instead of direct power supply, then the motor won’t get enough power. Thus it will overheat.

Another reason for the motor to get overheated is if the capacitor of the motor is damaged. If you have been using the compressor for a long time, this could be the possible reason.

Lights Dim in Starting

Most of the electrical power that a compressor takes, go to the motor. The motor of the compressor needs a lot of power to run.

Actually, the motor requires a lot of power to start and a little less to run. If the capacitor of the motor of your air compressor is damaged, then the motor takes in an unusual amount of power while starting.

This causes a lack of power in other components. As a result, the lights dim or they flicker when the motor starts.

Compressor Clicks & Stops

Sometimes, when you are about to start the compressor, you will hear that the compressor makes a clicking sound and then stops. Why does this happen?

It can be because of the pressure switch of the compressor. But it can also happen because of the motor.

If there is any problem with the centrifugal switch of the motor, then the motor will have difficulty to start. Thus, you will only hear a click and the compressor won’t run.

Compressor Just Hums

Typically an air compressor motor requires 120 V/AC power to run. To be more precise, the motor requires this power to start at first. But to keep running, a less amount of power is just as fine.

To gain this much power in the first place, every motor has a start capacitor. The capacitor works the same as a battery. It takes power and then supplies it to the motor.

However, if there is a problem in the capacitor, you will notice that your compressor will not run. Instead, it will only make a humming sound. This indicates that the motor of your compressor is getting power but not enough. That is why it’s humming instead of running.

Troubleshooting the Motor Problems

Replacing the Capacitor

The capacitor is the component that is used to control the amount of power that is supplied to the motor. The capacitor holds a certain amount of voltage and then releases it according to the motor’s requirement.

As you have already seen, the majority of the problems in a compressor due to the motor happens because of the capacitor. So, by replacing the capacitor, you can reduce a lot of air compressor motor problems.

To replace the capacitor here are the things you should keep in mind.

  • Choose a capacitor that has the same micro faraday rating as the one you used before.
  • The new capacitor should have the same voltage rating as the previous one.
  • Make sure your new capacitor has the same connectors as the old one.

Recommended Capacitors for Air Compressor Motor-

SUPCO SPP6 Relay/Capacitor

CPS 5-2-1 CSRU1 Compressor Saver

This is a good example of how to fix air compressor electric motor. But if there are internal problems in the motor, you can always rebuild or replace the motor to solve the air compressor electric motor problem.

Adding a New Centrifugal Switch

Most of the motors of an air compressor will have a centrifugal switch mounted on the shaft of the motor. But how do you know if your motor has a centrifugal switch or not? It’s very simple.

After turning on the compressor, keep the compressor running for a while and then turn it off. If your air compressor is working properly, then the motor will first slow down when you hit the off switch. Then the speed of the shaft will slow down, and you will hear a click. This shows you that your motor has a centrifugal switch.

The centrifugal switch actually helps the motor to consume power by measuring the cut in and cut out pressure. However, when this switch is damaged, the motor cannot take enough power from the source.

You can always replace this switch and make your motor run again with the required power that it needs. I recommend you to these switches-

Fetcus L14-152S Centrifugal Switch

L19-154S Electric Motor Centrifugal Switch

Using Rebuild Kit or Replacing the Motor

What happens if there is no problem in the capacitor or the centrifugal switch? Instead, the motor itself fails to start. If you face such a situation, you have two options to follow.

  • The first option for you is to rebuild the motor. You can use screwdrivers to open up the motor and check the inside. Sometimes, simply cleaning the inside of the motor will make it as good as new. And if you find any part damaged, you can fix that part and then close the motor. This is how rebuilding works.
  • And if there is no option for using an air compressor motor rebuild kit, you have to purchase a new motor and replace the old one. If you see your air compressor motor stopped working for good, replacing the motor is the only solution. Here are a few recommended motors that you can get for your compressor-

Hex Autoparts 5HP SPL Air Compressor Electric Motor

WEG 7.5 HP Air Compressor Duty Electric Motor

Finally, hope that this air compressor motor troubleshooting guide was helpful for you to find out the problem of your air compressor motor and fix it.

2 thoughts on “Air Compressor Motor Troubleshooting – 3 Ways to Fix”

  1. How do I wire a outlet plug onto a Emerson air compressor motor ? The plug has white black & green wires & motor has yellow red & brown.

  2. I have a Hitachi (Metabo) Compressor) attached directly to the motor, when I turn it on it hums, tried changing the capacitor and it still hums. Do you know what the problem?

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