Dryer stops early in mid cycle after running just 1,2 or a few minutes, randomly and in streaks. Sometimes runs for days with no problem, then it stops early every time. Dryer can ALWAYS be restarted IMMEDIATELY if I move timer to 'off' then reset it to run again.

After drying stops mid cycle, the timer becomes noisy, continues running, and it advances to the 'off' position very quickly, in any cycle, timed or moisture sensing. From 30 minutes it will go to zero in < 2 minutes.

After this mid cycle shutdown, the start button does not work correctly. Dryer starts, but stops as soon as the button is released. It will continue running only if the button is held down.

As mentioned above, turning the timer to OFF, then setting it to a run position again, allows the dryer to ALWAYS start again immediately. The start button works correctly. But it usually stops again very soon within 3 minutes, the problem repeats. Sometimes, not often, it will complete the cycle. This seems to indicate overheating is not the problem, as it always restarts immediately, sometimes quitting early, sometimes running to completion.

Timer behavior: If you set the timer to run, but never push start, the timer will wait 5 minutes doing nothing, then rapidly run down to zero all by itself, and makes a lot of 'gear' noise like a noisy electrc clock. This also happens if the drying cycle is interrupted (opening the door) and left for 5 minutes, the timer then winds down to zero quickly.

Problem continues after replacing control board.
Dryer still stops intermittently mid-cycle,
though perhaps, not as often as it used to.

The new board is better in this way:
It will enter diagnostic mode. The old board would not.

HOWEVER, the timer now runs much too slowly.
After running for an hour, timer moves only 5-10 minutes.
The dryer could now run all day if not monitored,
it must be turned off manually.

Thanks for your attention to my symptoms :)

Blower wheel is firmly attached, and no lint clogs found,
air moves freely,
firm air pressure is felt when pressing the outdoor exhaust vent louvers.
If overheating is the problem,
how can dryer always be restarted immediately,
after timer is set to OFF then set to run again?

I still have intermittent shutdown problem in any cycle,
can always restart immediately (not overheated).

Discovered I had reassembled the timer improperly after inspection,
with the motor upside down and gearwheel not meshing to the cam wheel.
It's meant to accept a different sized cam gear when turned 180 backward.
The gearwheel was pressing on smooth a surface of camwheel and timer advanced very slowly while improperly assembled.
Timer is now fixed and running in proper time,
and the normal very fast in diagnostic mode.

Does the thermistor control the drying temperature,
turning on and off the heater?
If the thermistor misbehaved and things got too hot,
won't something else trip and permanently shut down dryer?

I see there are to sensors inside the blower wheel housing.
One is the thermistor?
The other one is thermal fuse?
If that blows it must be replaced?

dear Eric,
Is this procedure reasonable to try:
First I believe the thermistor is a very low voltage / low current device.
True?

I want to very carefully short together the thermistor connections while dryer is running, to see if that makes the dryer stop with same symptoms I've been experiencing.
That would narrow it down better for me.

According to service specs, the thermistor should read:
9 ohms at 80 degrees,
2.5 ohms at 140 degrees,

so I assume:
shorted out = 0 ohms = very very hot.

This should not damage the control board I hope.
Normal operation is 20 ohms down to about 2 ohms,
shorted out is not a big change down to zero.

Thermistor was the cause. The plastic coating was gone, exposing the electronic sensor and wiring inside to moisture and dirt. Dryer has worked perfectly for weeks after installing new thermistor. I feel a little foolish for not examining the thermistor sooner, it was so easy to remove and look at it.