I have a whirlpool dryer that is a few years old. Soon after the warranty ran out the left side of the timer options quit working correctly. I never worried about fixing this and just used the "timed dry" option on the right side of the dial. This has worked for a few years until recently the dryer will run for a few minutes when I turn it on and then shuts off. The timer still keeps ticking and will sometimes come back on and then turns back off. Sometimes it runs longer than other times. I suspect the timer is the issue but see that the timer rarely goes out. The dryer is drying fine otherwise. I have found that if I apply pressure to the timer knob itself the dryer will run fine. Any ideas?
You have your hand right on the problem. Its the timer!
They go bad all the time. People turn them when the dryer is running and they turn them "backwards" while running. This arcs the contacts inside burning them out faster than normal operation would.
Replace the timer.
http://www.appliancepartspros.com/whirlpool-timer-snap-in-wpw10436303-ap6021393.html#
If you need more drying time, rotate the timer in the direction it normally moves itself. Go all the way around to get to where you want to set it. Always open the door or wait for the dryer to stop, before moving the timer knob.
Timer contacts sometimes arc and either stick closed or stick open in a portion of the timer rotation. A new timer will likely correct the problem. If you are really adept at repair of small devices you could possible dismantle the timer and find the problem area. There are several videos on you tube that show the details but it is harder than it looks.