Your disposer is equipped with a device called an overload protector. This device will turn the disposer off automatically if there is something wrong. If the disposer is jammed, if it is run for a very long period of time, or if there is something wrong with the disposer, it will shut down automatically.
Wrench and Reset
Make sure that the disposer’s switch is in the off position.
The overload protector is located under the sink, on the bottom of the disposer, facing the floor. It is a red square button. If the overload protector has tripped, you will see the red button dropped down about a quarter of an inch (5mm). Gently press the red button. If it does not stay up, wait ten minutes and try again.
If the red button still will not stay in, or the disposer requires repeatedly resetting the overload protector, the disposer may require service.