Dryer only stays on if you hold in the start button
Here are your parts
http://www.appliancepartspros.com/partsearch/modelsearch.aspx?model=110.60172002
See the attachment for the wiring diagram.
If you look at the wiring diagram you will see a switch just to the right of the motor. This is a centrifugal switch, is is supposed to change when the motor gets close to operating speed. It removes the motor’s start winding as leaving it in circuit would overheat the motor.
But it also provides a parallel circuit path for the start switch so that you can release the switch and the unit keeps running.
Sounds like it is not making contact to 6M.
Check that you do not have a wire off or a bad connection here.
Check that the motor is not clogged solid with lint.
You did not mention that the motor overheats but perhaps you have not let it run long enough.
The other centrifugal switch switches in the heater so that there is not heat without air flow.
You did not say if there is heat with the motor not running.
If this is the case then there is a problem with the mechanical parts of the centrifugal mechanism in the motor.
This may be that it is just clogged solid with lint.
Unfortunately you cannot just replace the switch you have to replace the entire motor.
AP3094245
Click on the picture for more info.