WARNING: The switch is supplied with 220V so one has to be careful not to get zapped. The first thing before doing anything is to flip the breaker to the pump switch and check it with a meter to ensure it is off.

Remove the small nut from the cover to gain access to the switch.

With the cover removed, check for power across the switch from supply lines L1 and L2 (Blue marker). Ensure that there is 0 volt.