How to Troubleshoot & Replace Whirlpool AP6008373 / WP3399639 Temperature Selector Switch

I replaced the cycling thermostat first...but that wasn't the problem. All other components (thermal fuse & high-limit thermostat) checked out. I couldn't find any video online that specifically dealt with testing the cycle switch; however, the diagram on the back of the switch indicated a resistance that should exist across two of the contacts; mine didn't read accordingly (with a multimeter)...so I rolled the dice and bought the cycle switch. That was indeed the problem. While at it, I cleaned all the lint paths, replaced the lint trap and lint chute seals, and installed a new belt. The bottom-line cost was cheaper than calling a serviceman, and my dryer is like new again! 

Replaced the switch 

Replaced high-limit thermostat, thermal fuse and thermistor and heating element. This created sufficient heat but other problem arose. Replaced timer and heat selection switch and all works fine now. Remember to clean out duct work while working on dryer -- obstructed duct work is a primary cause of blown fuses etc and if you don't clean it out you will just blow the new installed fuses as well. 

My husband determined it was the temperature switch, so we ordered one. It arrived just 4 days later, even with the Christmas holiday right in the middle. Reinstalled the switch...dryer is working great. 

Replaced the all known parts that can fail with this symptom. In reality, it was most likely thermal fuse...but I opted to replace multiple parts as a preventive measure. A key note: from the time of failure to the time my parts arrived was 22hrs! Appliance Parts Pros nailed the order and delivery like I have never experienced before. Did I pay more for parts than elsewhere? Yes, but their service, support, database, parts diagram and diagnostic tools and suggestion were well worth paying for vs struggling on my own. Many thanks!!! 

The fix was quick and easy. 

So, I ordered the timer and temperature switch to replace the bad ones. I was able to install them fairly easily. I just pulled the back cover off of the dryer and changed out the two switches. All the wiring was set up in a way that I couldn't mix up any connections. I spent more time on cleaning out the lint duct and replacing the exhaust duct because I hadn't done those in a while. I was able to get it all changed out and cleaned up for the weeks laundry. 

Unplugged dryer from wall, removed dryer vent from back of unit. Took a Phillip's head screwdriver (drill) removed metal panels on back on dryer. Pulled every part that had to do with heat and tested it for continuity, revealing the Temperature Selector Switch as the culprit. Bought the part here and grabbed a few extra parts to have on hand. Parts were here in 3 days. Popped the new parts in, plugged the wire harnesses in, screwed everything back together. Super easy to fix! 

Replaced parts ordered. 

I took top rear panel took out old switch, and replaced it with new one.