How to Troubleshoot & Replace Frigidaire AP2107778 / 131873500 Timer Knob

Replaced knob. Works beautifully now. 

I am happy. This was a VERY quick fix. Timer knob broke Sat., 8/30/14. After being unable to find/get it locally, a friend recommended AppliancePartsPro. I found my part and ordered it Sun., 8/31/14. Delivered Wed., 9/3, and a PERFECT fit! Your site is the ONLY one that gave both front and back pictures of the timer knob *and* a diagram showing where it fit on the Frigidaire dryer. This is how I discovered that I had selected the wrong timer knob. The other one is the exact same size but has a different back/shaft. 

I had to order another one at $30.00. The piece that broke is plastic so ten years old I guess they can get brittle. I also used the Chat online, which worked really well and fast! She found my replacement part and we ordered and was done in a matter of minutes.