We replaced all the parts involved with heat generation: burner assembly, ignitor, flame sensor, thermostat, thermal fuse, and thermal cut-off. Likely only one of these parts was the cause however I chose to replace all since the dryer is 20yrs old and likely the other parts would malfunction soon. The repair was easy: videos on AppliancePartsPros.com for each part were excellent and very helpful. One tidbit: the exhaust fan assembly was clogged with lint so I suspect this was the ultimate cause of the failure of one of the parts, likely the thermal fuse. I will make a point to clean out the exhaust assembly yearly from now on... fire hazard! AppliancePartsPros.com is an amazing place to do business... prices are a bit higher but well worth it because of the parts in stock, extremely fast delivery, and teaching videos for each part. Thank you, APP!