Troubleshooting an Auger Motor

What is an auger motor?

The term “auger motor” refers to a device, consisting of an electric motor and a reduction gearbox, that turns an auger shaft at a predetermined rate to deliver fuel from the hopper to the burn pot in a pellet stove. The control board, after analyzing data received from several switches and sensors in the stove, completes the electrical circuit to the auger motor. There are many types of auger motors used in pellet stoves. The two most popular auger motors in the US are of the shaded pole and the synchronous varieties.

image Shaded-Pole Gear Motor – uses a standard c-frame electric motor, turning at a high rate of speed, to turn a set of gears which turn the auger at a constant, much slower rate with much higher torque.

You can test the torque of your auger motor by using a pair of channel lock pliers to try and stop the rotation of the motor shaft. If you can easily stop the motor shaft from turning, the motor is weak and should be replaced. Most auger motors of this variety put out between 16 and 20 ft/lbs of torque.
image Synchronous Motor – turns at a rate directly related to the frequency of the AC current input. They are highly efficient and quieter than standard c-frame motors. These motors are typically mounted to a smaller gearbox and put out between 5 and 10ft/lbs

Note: This type of motor often relies on a capacitor to store power for use during starts under load. If your motor has a capacitor, you will need an adapter to include the capacitor when bench testing with a test wire. Failure to engage the capacitor can cause irreparable damage to the motor.Do not test with pliers. Use finger force to test weakness.

How to Test an Auger Motor

Most auger motors in the US run on 115-120VAC. This testing sequence works for these two specific motor types. Using these steps on other types of motors can cause catastrophic failure and/or personal injury or fire. You must remove the motor from the stove and perform a bench test. Bench testing is a reliable way to test motor performance because it is isolated from the rest of the stove.

Tools you may need:

- Surge protector

- Test wire with adapters

- Channel lock pliers

How to Bench Test an Auger Motor

  1. Turn off the stove, unplug from the wall, and remove the auger motor from the stove.
  2. Connect the motor to your test wire, using adapters if needed.
  3. Make sure the surge protector is switched “OFF.” Plug the test wire into the surge protector [refer to our tutorial HERE for help making your own test wire].
  4. Switch the surge protector to “ON.” The motor should immediately begin to turn.

This video tutorial will walk you through the steps of testing the auger motor:

Frequently Asked Questions:

What causes the auger motor to over-feed pellets?

Auger motors turn at one constant speed. They pulse on and off when the control board sends power to the motor. Adjusting the feed rate on your control panel tells the motor to run either increase or decrease the frequency of feed cycles. This controls the flow of pellets without changing the speed at which the auger motor turns. An auger motor that feeds too much is usually a symptom of a dirty stove or a faulty control board.

Should the output shaft spin freely?

You should NOT be able to turn the output shaft by hand. If the output shaft spins freely, the gearbox has failed and the auger motor should be replaced.

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