Product review (5 stars): Fine replacement for the 3399693
Was looking to replace the thermostat on an older Whirlpool dryer. After having no luck finding an exact replacement for the FPS P/N 3399693 thermostat, I decided to take a chance on the  3977767 thermostat. The new one is a bit smaller than the older one, but it fit just fine. And I'm happy to report it works just fine as well! For less than 8 dollars, I'm hoping to get a few more years out of my dryer.