Replacing the Thermostat in a Kenmore Series 90 Dryer (Electric) Made by Whirlpool

If your Kenmore Series 90 Electric Dryer (110.60922990) is running hot and you cannot select cooler temperatures, it is likely that the thermostat (cycling thermostat) is bad. Fortunately, it is easy to replace. Unfortunately, it happens far too frequently. This dryer is on its fifth thermostat in about 20 years. Since I was going back in again, I decided to document it. The current cost of the thermostat is about $30.00 USD.

The badges say Kenmore but the guts are all Whirlpool (FSP parts).

Check the “Other sensors behind the access panel” section of this Ible for the two other sensors behind the access panel. They can be responsible for the dryer not heating/

Remember, UNPLUG THE DRYER BEFORE YOU DO ANY WORK ON THE DRYER.

Parts

For this dryer, order the genuine Whirlpool dryer thermostat 8318268 / WP8318268. Always check your dryer model for part compatibility before you buy.

Tools

A stiff (thick) putty knife or two flexible (thin) putty knives.

A 1/4” drive breaker bar with a 1/4” socket

A vacuum with hose attachments

Currently, there are explosion diagrams located at http://www.searspartsdirect.com/model-number/11060922990/0582/0151200.html

UNPLUG THE DRYER BEFORE YOU DO ANY WORK ON THE DRYER. There is a shock hazard if it grounds through you, a fire hazard if you short it out, and a hazard to other components if you short it out. So UNPLUG THE DRYER BEFORE YOU DO ANY WORK ON THE DRYER.

Remove the lint trap.

My favorite disclaimer is from the author Samuel M. Goldwasser (Disclaimer) - ”We will not be responsible for damage to equipment, your ego, blown parts, county wide power outages, spontaneously generated mini (or larger) black holes, planetary disruptions, or personal injury that may result from the use of this material.”

Slide a putty knife in at one of the top clips. Keep the putty knife against the bottom of the front panel of the dryer, not the top of the access panel. Press the putty knife until it contacts the back edge of the dryer panel. The top edge of the access panel will pop outward when the clip is disengaged. Repeat for the second clip.

You can see the top clips if you look into the gap between the dryer panel and access panel

When both the top clips are undone, tilt the access panel forward and slip it off of the bottom clips.

Remove the two screws on the upper left and right of the duct and slip the duct out. Be aware that there is a clip on the lower left end.

Clean out the lint buildup. This usually requires wet paper towels to dislodge the lint. Watch out for sharp edges.

Remove the two screws on the upper left and right of the blower shroud. Clean out the lint buildup. Vacuum the inside of the dryer. There isn’t precision sealing so some lint always escapes into the cabinet.

You may be surprised by how much lint carpets the inside of the cabinet and the heater element is located within this same space. The U.S. Fire Administration (https://www.usfa.fema.gov/prevention/outreach/clothes_dryers.html) recommends cleaning your lint filter and duct to prevent fires. You may want to add cleaning the cabinet to the list.

Locate the thermostat (four leads). Remove the left and right screws. It is a tight fit on the left screw but the socket and breaker bar will fit. Swap the leads from the old thermostat to the new one.

Reverse the disassembly steps to reassemble. Make sure the gaskets are lined up or you could end up with the dryer venting into the cabinet and greater lint buildup.

If you were wondering what was inside the sealed thermostat, not much. A circuit from the side terminals identified as a “heater” circuit and a circuit from the end terminals that turns the dryer’s heater element on and off.

The thermostat is a simple bimetallic cap that deforms inward when heated. When it deforms, it pushes the plunger against and lifts the spring arm. The contacts are disconnected, the circuit is broken, and the heating element is turned off. When the cap cools sufficiently, it reforms and allows the plunger to move back. The spring arm closes, the contacts are connected, the circuit is made, and the heating element is turned on.

There are two failure modes.

The contacts fail to close and the dryer will not heat. You will find no continuity on the end terminals if you test it.

The contacts fail to open and the dryer will constantly heat. You will find continuity on the end terminals if you test it.

Every time the dryer lost the capability of selecting temperatures, it has been #2.

Applianceaid.com has a good example of how a dryer thermostat works.

http://www.applianceaid.com/how-dryer-thermostats-...

The other sensors behind the access panel are the:

1. Dryer thermal cut-off fuse

2. Dryer high-limit thermostat

According to the literature, when tested with the leads removed, there should be continuity. An open condition causes a “no heat” condition.

The high-limit thermostat on this dryer only failed once.