Model #LA7780XSW1, the dryer would not start when the button was pressed and no matter of coaxing by the customer would get it to work. The dryer had been working fine all day, but after several loads, it just wouldn't work anymore. Thinking it just needed to cool down, the customer tried again later in the day but no joy. There was still more laundry to do so this dryer needed some quick attention.



The motor dryer circuits on many of the more common models in use are quite similar in their layout and operation. The names of the dryer parts may change and the colors of the wires are rarely the same, but the way voltage gets to the motor is oddly familiar once you get to see a few of them. The simple path, as shown in the sample wiring diagram, is from the terminal blocks L1 connector through the timer (it could also be an electronic control board), the start button, then to the door switch, the safety thermal fuse, then finally to the motor. So as you can see, the components that have the potential to prevent the motor from starting are few, and each can be tested to determine which component has failed.

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When I visit a dryer that will not start, I will always begin by verifying the problem and I will listen to the unit during this process. If the start button is pressed and any noise is found to come from the dryer motor, then our problem is different than what I am outlining in this post, but more likely a motor failure, or some mechanical failure. If I don't hear any noise, then I can be confident, it has something to do with getting voltage to the motor.

When I check components, I begin by playing the odds as to which item may be at fault. Even though I have limited the failure items, some are easier to get to and test than others so I will start with what is easy and more probable, and then work my way to the more difficult and less likely. The quickest thing to get to and a very likely failure is the door switch. This will open the motor circuit when the door is open and if the dryer has a drum light, with turn on the light at the same time. By opening the door, it is possible to actuate the door switch and listen for the familiar click of the contacts. If the switch doesn't click, or the light stays on when actuated, then it has failed.

My next component is the thermal fuse. A bit more difficult to get to, but the most likely item to fail. It will usually be attached to the blower outlet of most dryers and is designed to open the circuit in the event of an over temperature condition. Simply bypassing this fuse is a quick way to determine its condition and no meter is required. Just remember this is not an appropriate fix as safety components are there for a reason and bypassing them even to just get another laundry load dried is asking for trouble.

Next is the timer or electronic control. These are very unlikely failure points due to their overall reliability, but they can fail. A multimeter is best used to test them by simply looking for voltage going to the component, then back out once the knob is turned, or the start button pressed. Also near the timer would be the start button. This too can be checked using a multimeter in much the same way the timer and control boards are checked.

The final suspect would be the motor. They do fail and I have plenty lying around to prove it, but most require more dissasembly then I want to get into so I save them for last. Using a multimeter again, if I find voltage going to the motor but no operation, the motor is bad. Double check by doing a resistance check of the motor windings and you can be confident in your findings.

On this dryer, I started with the door switch, which operated with an expected click so I went on to the thermal fuse. Removing the rear panel takes only a few moments and once there, the thermal fuse is front and center down low on the blower housing. I prefer to use my meter to do electrical tests, but as I said above, bypassing the fuse and pressing the start button will work and when I did, the dryer motor came to life. Looks like I found my failed component.

My next step was to replace the thermal fuse and reconnect both wire connectors. With the unit plugged back in, starting a drying cycle showed this unit was again ready for use. But this was not the final repair for this customer. The thermal fuses in dryers are designed to open in the event of the over temp situation. This can be caused by the operating thermostat going haywire, but more likely is a restricted dryer vent causing the dryers internal temperature to spike instead of maintaining at a more consistent level. A look into the vent revealed a significant lint buildup and the airflow to the outside of the house was little if any. This vent was plugged and needed to be cleaned. Fortunately, I can fix that too.

So after some quick trouble shooting I was able to treat the symptom by repairing the dryer, and solving the problem by cleaning the vent. Some brief education for the customer about the problem and ways to prevent a repeat performance and I was on my way.

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