How to Troubleshoot & Replace Whirlpool AP6014307 / WP9830714 Dryer Timer 5-Cycle

Replaced timer 

I had made a temporary repair to Timer's high current feeding the heater circuit months ago when the eratic heating issue began. These contacts were practically gone with well over 12 years of operation. The temporary repair lasted four months but when the eratic heating crept up again I decided it was time to just replace the timer. With the new timer installed the heater was working normally but another problem showed up shortly afterwards. The timer would not complete a cycle, regardless of which mode was selected. It stopped for no apparent reason but would restart again when the start button was pressed. I thought it might have been the centrifugal switch on the motor but then decided to check the door switch since it is easier to access and test.I was able to confirm intermittent contact closure of the door switch with the plunger depressed using the diode test function on a Fluke 27 DMM. I removed the switch, took it apart, and cleaned up the contacts which had obvious damage from years of use. I then reassembled the switch and installed it back into the dryer. Problem solved, but I will probably order a new switch since I had to remove quite a bit of the contact material and also the original surface plating.