, this unit started the first time for the customer, but would only make a humming sound the next time they tried to use it. Figuring there must be something wrong with the motors start winding I proceeded to do a bit of troubleshooting.Starting a Dryer Motor
The electric motors used in dryers rely on a start winding along with the motors normal run winding to get the motor started with a heavy load of clothes. Once the motor gets up to speed, the start winding is no longer needed and is removed from the electrical circuit by the action of the centrifugal switch opening. This switch is attached to the motor and can be heard as a snap or click when the motor starts or stops. Once started, the motor will continue to run using only the run winding until the unit is once again stopped causing the centrifugal switch to close. With the switch closed, it returns the start winding to the circuit and is ready to start the motor again.The Test
The trouble shooting steps for a bad start winding is a simple matter of holding the door switch closed while pressing the start button, and spinning the dryers drum to give it a kind of push start. If the unit takes off running, the start winding, or centrifugal switch has failed. If the unit doesn't begin to tumble, it's time to look at the circuit and see what you may have missed. But in the case of this dryer, the drum started working, verifying my suspicion. The next step was to get to the motor and do a resistance check of both windings to verify if it is the motor itself or the switch that is causing the problem. An open run or start winding would indicate a motor failure, but if they check OK, the centrifugal switch contacts can be checked for continuity to verify there operation.Problem Resolution
The motor on this dryer had a couple of the motor winding leads out of place resulting in the centrifugal switch hitting and breaking them the first time the motor started. That is why this dryer worked the first time only. Installed a new motor for the customer and now the dryer starts every time.
Drive Motor Part # 131560100