I could not find any tech info on this unit so the below is just an example and may not be a match for your unit.
http://www.applianceaid.com/whirlpool-dryers.html

Take a look at Item 34 Wiring Diagrams and then Item 9 Newer Style electric.

You will see that the motor has 2 centrifugal switches on it (5M/6M and 1M/2M). These switches close when the motor gets close to operating speed,

1M/2M switches in the heating coil. This ensures that the heater does not come on till there is air flowing over it.

5M/6M switches out the start winding as leaving it on all the time will over heat the motor.
Also it is in parallel with the start switch so it keeps the motor running after you release the start button.
This switch is probably your problem.

Could be:
1. A wire has come loose
2. The switch is toast
3. The centrifugal mechanism is not working. If the heat does not come on when you hold the start switch in then this is the most likely cause. May be that t is just clogged solid with lint.

The latter 2 probably will require that the motor be replaced as most units do not let you just replace the switch.
You will have to call/email AppliancPartsPros to confirm this.