First, opened up the top portion of the dryer. This dryer was a used GE model bought at a yard sale 3 or 4 yrs ago. Found that the timer motor wasn't working, and used a multimeter to determine was this was the problem. Bought that part from AppliancePartsPros.com. Put everything back together and nothing happened when the start button was pushed. Hmm. So looked at the Timer knob itself & found the plastic was cracked where it fits onto the motor shaft. We put a zip tie cinch on it to allow the timer knob to fit on the shaft better, but still wouldn't work ( didn't hear a familiar click sound as the knob was turned through the time choices on the dial). So then wondered if the new Timer wasn't working. Nope, it was ok. So looked at the motor shaft, which looked different than the original, and wondered if the new shaft needed a new Timer knob that would fit it more correctly, as it was an old machine. We sent for a new Timer knob & yay! It worked! Knob made familiar clicking noises as the drying time choices were made. Back in business!