Model #LDE5750W0, this older model electric dryer would no longer tumble for the customer, but instead, would make a loud buzzing noise then the start button was pressed. The drum could be turned by hand with some resistance so they figured the belt was still attached to the motor, but it just wouldn’t start. Even holding the door switch closed and trying to spin the drum while holding the start button wasn’t working. It’s an old dryer, but it has been working well, so the customer decided to try for service and see if they could keep from buying a new one.
The wiring is most dryers is quite basic and there are few dryer parts that can actually prevent the motor from running. Normally, the motor circuit will contain the motor itself, a thermal fuse for safety, a push to start switch, and the timer. Any one of these can keep the motor from running, but the resulting symptom will be nothing happens when the start button is pressed. Because this unit would make noise instead of starting, it would appear to check out electrically, which leave the possibility of a mechanical failure. But this too didn’t seem to be the problem since the drum could be rotated by hand. Time to take a look inside.
With the front panel removed and the drum out of the way, the age of this unit became apparent just by looking at the amount of lint resting in the bottom. This is far from unusual, and a good example of how some preventative maintenance can possibly prevent a bigger problem down the road. I bypassed the door switch so I could start the dryer and visually verify the problem which is shown in the video below. The motor would spin freely by hand, but would not start by itself.
Some testing with the help of my multimeter found both the run and start windings of the motor where complete circuits and I did have voltage to the motor, just in case the noise didn’t clue me in. Since there was nothing mechanical stopping the motor from turning, this left the centrifugal switch as the likely problem. The switch does two things. It keeps the start and run windings in the circuit to aid in getting the motor running, until it reaches about 750rpm, then it takes the start winding out of the circuit, and it completes the L2 120vac circuit to the heating element. The switch setup allows for better motor starting and prevents the heater from operating unless the motor is operating.
After removing some excess lint and such from the motor, I removed the screws holding the centrifugal switch to the motor and again using my meter, checked the switch contacts for operation. What I found was the contacts to the motor windings were damaged for the run winding, which meant the motor was trying to start using the start winding alone. I attempted to clean the contacts with my jewelers files, but they were to far gone. The solution was going to be a new centrifugal switch.
Given the age of this machine, I wasn’t to shocked to find the part number for the switch substituted over to the entire dryer motor which is a bit more expensive to replace. The customer really didn’t want to put the labor and the cost of a new motor into this old machine, but after making a phone call, I was able to locate a suitable switch to complete this repair. The customer was happy to have the dyer working again, and I was glad to have another customer success story.