The Kenmore 70 Series heavy duty dryer can be a pretty good dryer for many homes. It is simple to operate, has an easily-accessible lint trap, and can run on 120 volts. However, one problem that may occur with it as the dryer gets older is that it keeps running after its cycle has finished. When it completes one cycle, it will stop, but if it is left alone it will continue on to the next cycle and start that one. It will keep running until someone notices and unplugs the dryer or leaves the door open, and it will drain electricity and cause possible damage to your laundry.
Usually the problem can be fixed fairly easily if you don't mind getting your hands a little dirty (figuratively). The problem is likely nothing more than a faulty switch. The switch (which sits behind the button you press to start the dryer) relies on a piece of copper to make and break the connection, and this copper piece can become bent or warped over time. This article will walk you through repairing that switch. (These instructions were written for the Kenmore 73742 dryer, but the procedure should be similar, if not identical, for the other 70 series dryers.)
The very first thing to do is to unplug the dryer from the outlet so it is not getting any power. Once it is unplugged, you'll need to either pull the dryer out, away from the wall, or tilt it forward so that you can get to the rear access panel. Ideally you should pull the dryer out, but there's not always room to do that. If you tilt the dryer forward, place something sturdy in front of it and underneath it so that there is no chance of the dryer falling either forward or backward and causing harm to anyone in the area or causing damage to the dryer or other appliances.
The switch in question is located behind the dryer's start button (on the right side of the operation panel). To get to the switch, you need to remove the rear access panel, which is a long metal cover that runs across the upper length of the dryer and is held in place by six slotted screws. Set the screws and the cover somewhere safe and out of the way.
As you're looking at the back of the dryer, the switch will be on your far left. It is a small black box with several different wires attached to it. All of the wires can be pulled off (by pulling on the connector, not the actual wire) though if they've been on there for a while you may need to use a pair of needle-nose pliers to (gently) pull them off. Before removing the wires, it's a good idea to either mark the individual connectors or to take a picture of the switch assembly, so that you know where each wire goes when you reattach them.
Once you've removed the wires, you can test the switch if you have a multimeter handy. Set it to the logic or continuity setting (if it has that feature). If the multimeter is on the right setting, you should hear a beep or see the display change when you touch the two leads to each other. Place one lead on either of the upper contacts (the two that come out of the same copper strip) and the other on the lower contact below them, and then push in the start button on the front of the dryer.
Normally you would see a change of state in the switch, signalled by either a beep or a change on the multimeter's display. However, if the switch is causing your dryer's problem, you won't notice any change on the multimeter when you press the start button.
You can take the switch apart without removing it from its housing, which means one less step when you put it all back together. To take apart the switch, pry the back off with a small flathead screwdriver or a pocket knife. If you can pry one side up a little bit and then work on the opposite side, it should pop right out.
The start button has a spring that sits between the button and the switch; make sure you don't lose this spring when the switch comes off. When you have the switch removed, turn it over to look at the inside. There is a bent copper strip running along one side -- this is the culprit causing your problem.
The copper strip over time has become bent so that it is always in contact with the switch. All you have to do is bend it away from the switch's contact enough so that it doesn't rest against it when you reinstall it, but still leave it close enough to make the contact when the start button is pressed. This will require some trial and error -- bend it a little, reattach it, and test the start button while your multimeter is attached to the two contacts. When you have the copper piece bent enough so that the switch changes state when you press the button, you've fixed the problem.
Now put everything back together. Reattach the switch wires, screw the rear panel back on, push the dryer back to its original position, and plug it in. Then test it by turning it to different settings and making sure it doesn't come on unless you press the start button, but also make sure that when you press the start button it actually starts. If both of those things happen, you have successfully fixed your dryer!
(Originally published on Helium.com, September 2010)
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