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How to Fix a Motor

Your small electric motor works by having electricity flow through bare wires to generate magnetism. This magnetism rotates a motor shaft. Motors can go bad and need repairs. Repairing a motor can be complex, but it's not so bad if you follow simple instructions.

Unplug your motor and discharge the capacitor before you begin work. Make a discharge tool by clipping your jumper to the leads of a resister, and clip the free probe of your jumper to a blade on a screwdriver.

Lubricate all the moving parts with an SAE 20-weight motor oil. If your motor has oil cups, fill them to the top.

Check your bar-to-bar commutator. Set your volt-ohm meter on RX1, and touch the probes to the adjacent bars all around the commutator on the end of your motor. All your readings should be about the same. If you have an unusually high ohms reading, you likely have an open circuit. If you get a zero reading, there's a short in that bar.

Probe the field coils on your motor. Set your volt-ohm meter to RX1 and clip the probes to the field coil leads. High ohms or infinity indicates an open circuit. The motor in multispeed appliances will have several field coil leads.

Look for damage or wear on the housing brushes. Remove the brushes from the housing and check them out. Replace the brushes when they're shorter than they are wide.

Check your brushes to make sure they are fitting properly. Your brushes should move freely in their housings. Replace any springs that appear to be weak. Clean the housing and the brushes with contact cleaner.

Polish your commutator if it appears rough. Hold fine sandpaper around your commutator and turn it. Then burnish the bars with hardwood stick.

Things You Will Need

  • Screwdriver
  • Sandpaper
  • Volt-ohm meter
  • Contact cleaner

Tips

  • If your motor smells burnt or like hot oil, your motor is overheating. This is a problem that is caused by overheated winding insulation or by friction in the motor bearings or drive components. If this happens, lubricate your motor immediately, so you won't have to replace the entire motor.
  • If your motor is too hot to touch, your motor is in dire need of repair. A motor that is running properly will get warm but not hot. If it's hot, the air intakes may be clogged with lint or other debris, keeping the fan from getting cool air over the windings.
  • If your motor is grinding, your bearings are worn out and need replaced. If it's squealing, you should lubricate the bearings to keep it from causing damage to your motor.

Warnings

  • Disconnect any motor from its power source before you work on it or service it.
  • Do not work on an electric motor when it's wet. Let it dry first.
  • Make sure your grounding wire is connected properly before you restore power to your electric motor.

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