Question: How do you test and troubleshoot the motors, transformer, and relay?

Answer: We strongly recommend that a professional vacuum specialist follow these directions to trouble shoot components. You can locate a local dealer, mail your unit to MD, or visit a vacuum repair center.

Test and Troubleshoot Motor: Gain access into the motor area then smell the motor. If you detect a strong odor (the shellac that coats the copper coil windings when the motor is burning or burnt out) then the motor is bad and needs to be replaced.

Second, if there is no odor then you will need to turn the vacuum on and observe the motor. If the motor is out, carefully hot wire it with direct 110 volt leads. There are two leads going to the motor - one black and one white or two black. Use these wires and ignore the green one if there. 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 (motors are not polarity sensitive). If the motor is outside the vacuum unit you will need to disconnect the motor wires from the unit to isolate the motors. Be careful when you have live voltage at the end of the alligator clips - don't touch them or touch them together or let them touch any metal. If the motor is good or just about bad, this will work. But if it is going bad it will work for only 10 or 15 minutes, sometimes for only one minute. If it doesn't start at all it is obviously bad. Sometimes slapping the vacuum unit will jar the motor and get it to work again for a few minutes. A replacement motor(s) will be necessary.

From experience, relays and transformers rarely go out. It is usually the motor that burns out and it usually does so quickly when at life's end. Take the time to check all of your wire connections - hours can be spent diagnosing a vacuum only to find out it is a bad connection.

Check and Troubleshoot Vacuum Motor Brushes: With the motor running, you will want to inspect the commutator - the center of the less wide part of the overall motor where the two motor brushes (thick graphic / lead looking parts) touch the inner rotating copper armature. It is normal for there to be a slight blue spark right at the carbon brush on the commutator - but if the blue spark is large and wrapping around the commutator then you will need to replace the carbon brushes if the motor bearing are still solid. Test that by turning the motor off and pushing on the center shaft, the armature. If it has any play besides spinning then replace the motor. If solid then replace the brushes - instructions here. Motor brush "lead" is around 3/4 inch when new. When it gets low - around 3/8 inch it must be replaced. If it gets too low and scores the commutator, replace the motor. If the copper commutator is seriously damaged - totally blackened and rough - replace the motor.

Test and Troubleshoot Vacuum Transformer: Older vacuums had a separate relay and transformer. Newer ones have all the electronics and one circuit board. On a separate transformer there will be a total of four wires - the black and white are the power coming in and the two 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 get a small low voltage spark by touching the blue and yellow wires together. No spark means the transformer is bad. We have several transformers but they are not for all vacuums. They work for vacuums with a similar set up as pictured below and are available here under electronics and transformers.

Test and Troubleshoot Relay: Older vacuums had a separate relay and transformer. Newer ones have all the electronics and one circuit board. Our replacement relay will only work for similar wired vacuums as pictured above. A relay has contact points that can go bad but can be tested. 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". If you put the wires on the wrong terminals there will be no damage. The replacement relay we sell is part #242 and it replaces the one above and some others. The relay is available here in electronics and relays.

Test and Trouble Shoot Vacuum Circuit Boards: 

1. Ensure that you are powering up the board with the proper voltage (120 or 240).
2. Attach the power cord white wire to the “Neutral" (NTL) connection.
3. Attach the black power cord wire to the “power in" or “line" connection.
4. Plug the power cord into your power source.
5. Now arc a wire across the low voltage terminals.
6. You should see a spark when you touch the terminals and you should hear a “click" inside the board.
7. If there is no spark, then the transformer is bad. If there is no spark and you do not hear a “click" then the relay is likely bad. Either way replace the entire board.
8. If you do see a spark and hear a “click" then you want to test 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. (240 volt output cannot be tested on a 110 volt appliance.) If the electronic device does not run then you have a bad relay and the board needs to be replaced.

Our boards are made by Alutron as most all other vacuum manufacturers are. Our boards can be used to replace other brands as the basic functions are exactly the same. The mounting may be a little different and there are no idiot lights (which are really not needed as they are based on hours ran, not truly helpful data). Here is a sample circuit board and they are available here under electronics and vacuum circuit boards.