How to know if my vacuum motor is bad?

Need to test or troubleshoot a vacuum motor or even a relay or circuit brush? You may find the necessary steps here.

We suggest entrusting the troubleshooting indicated below to a vacuum professional. You may find a local dealer or contact us for recommendations in your area.

How to Test and Troubleshoot a Central Vacuum Motor

What Does it Mean When You Hear a Click When You Try to Turn on the Vacuum?

• If all you hear when you attempt to start the vacuum motor from inside the home is a click, the vacuum unit’s motor is dead and has to be replaced.

Strong Smell from the Vacuum Unit

• A strong odor from the shellac on the copper coil windings indicates that the motor is going to or has already burned out.
• If the motor is still running, even if it turns on and off by itself as it is heating and cooling, you can still run the motor until it gives up for good. Note: If the thermal mini breaker burns out, you’ll need to replace it or the whole circuit board it’s on.
• If there is no odor, you should switch on the vacuum and inspect the motor. If you see lots of blue sparks, read about the motor brushes below.

How to Hot Wire the Vacuum Unit

• If the vacuum unit’s motor is removed, carefully hot-wire it using direct 110 volt lines.
• There are two leads going to the motor – one black and one white or two black. Utilize these wires and disregard the green one if it exists.
• Hot wire with a patch cord (an AC cord with a regular electrical plug on one end and two alligator clips on the other end) and hook one lead to each of the motor wires (motor wires are not polarity sensitive). Make sure the motor is elevated so that air may enter the bottom of the motor.
• If the motor still has some life in it, it will start, but if it is failing, it will only run for around 10-15 minutes. That is definitely awful if it does not start at all. Slapping the motor or vacuum unit may sometimes shock the motor and get it working again for a few minutes. Motors that operate intermittently should be replaced.
• Relays and transformers seldom fail in my experience. It is usually the motor that burns out and it usually does so quickly when at life’s end.

Always Test the Vacuum’s Wire Connections

• Check all of your electrical connections – hours might be wasted troubleshooting a vacuum only to discover it was a poor connection.

How to Check and Troubleshoot Vacuum Motor Brushes

Inspecting the Vacuum Commutator for Motor Brush Problems

• When the motor is operating, examine the commutator, which is located in the middle of the less broad area of the overall motor where the two motor brushes (thick graphite / lead-looking components) make contact with the inner revolving copper armature.
  • It is usual to see a little blue spark near the carbon brush on the commutator.
  • If the blue spark is huge and snaking around the commutator, the carbon brushes must be replaced, but only if the motor bearing is still firm and not wobbling

• Turn off the motor and press on the central shaft, which is the armature. Replace the motor if it has any play other than spinning. Replace the brushes if they are solid – motor brush replacement instructions.

How to Know Your Motor Brush Needs to Be Replaced

• Motor brush “lead” is around 3/4 inch when new. It must be changed when it reaches 3/8 inch.
• Note: If it gets too low and scores and damages the commutator, replace the motor. Replace the motor if the copper commutator is severely damaged (completely blackened and rough).

How to Test and Troubleshoot a Vacuum Transformer

How to Troubleshoot a Vacuum Transformer on a Circuit Board

• A separate relay and transformer were used in older vacuums. All of the electronics in newer models are housed on a single circuit board. On a transformer apart from a circuit board, there will be a total of four wires or more – the black and white are the power/neutral coming in and the colored leads (usually blue and yellow) are the 24 volts going out.
• Do a simple test by putting the black and white wire to 110 volts, then see if you get a small, low voltage spark by touching the blue and yellow wires together. If there is no spark, the transformer is faulty.
• We have various transformers, however not all of them are suitable for all vacuums. They work for vacuums with a similar set up as pictured below and are available here under electronics and transformers.

How to Test and Troubleshoot Vacuum Relays

How to Test a Vacuum Relay on a Circuit Board

• A separate relay and transformer were used in older vacuums. Later models have all of the circuitry on a single circuit board. Our replacement relay will only work for similar wired vacuums as pictured above. A relay has contact points that may fail, but they can also be checked.
• When you apply 24 volts (from the transformer) across the low voltage side of the relay (the side with a small copper wire leading up to the terminal posts) then the relay should “click”. There will be no harm if you connect the wires to the incorrect terminals.
• The replacement relay we sell is part 242 and it replaces the one above and some others. If you are replacing the relay with 242 then you will also have to replace the transformer with the more powerful model. The relay may be found in electronics and relays.

How to Test and Troubleshoot Vacuum Circuit Boards

1. Check that the board is receiving the correct voltage (120 or 240).
2. Connect the white wire from the power cable to the “Neutral” (NTL) connector.
3. Connect the “power in” or “line” connector with the black power cable wire.
4. Plug the power cord into your power source.
5. Now arc a wire across the low voltage terminals.
6. When you contact the terminals, you should see a little spark and hear a “click” within the board.
7. If there is no spark, the transformer is defective. If there is no spark and no “click,” the relay is most likely faulty. Replace the complete board in any case.
8. If you see a spark and hear a “click,” you should check for voltage output. Attach any 110 volt electronic device (or functional vacuum motor) to the output terminals – “Motor Neutral” and “Motor Power” for a complete circuit. (A 110 volt appliance cannot be tested for 240 volt output.) If the electrical equipment does not work, you have a faulty relay and the circuit board must be changed.

Alutron, a frequent supplier for numerous vacuum manufacturers, manufactures our boards. Our boards may replace other brands since their core functionalities are the same. The mounting may vary somewhat, and our board has no idiot lights. These lights are unnecessary since they are based on hours of operation rather than actually useful data. A sample circuit board may be found under electronics and vacuum circuit boards.

Related Questions

• What causes a vacuum motor to burn out?

  Overheating is the most prevalent cause of vacuum motor failure. A flow-through motor is used in the majority of ‘dry’ vacuums. These motors use the air they have sucked up the dust with, to cool themselves. When there is a blockage, flow-though motors are unable to cool themselves due to the lack of airflow.

• Is it normal for a vacuum motor to spark?

  Motor can run.
  A tiny blue spark immediately at the carbon brush is okay; however, if the blue spark is huge and wraps around the commutator, the carbon brushes must be replaced (if the commutator on the armature is seriously damaged, you will need to replace the motor).

• How do you test a vacuum motor?

  Turn off the motor and press on the central shaft, which is the armature. Replace the motor if it has any play other than spinning. Replace the brushes if they are solid – motor brush replacement instructions.