What is showing 6 volts? and does it have anything to do with the power to the pump?
The pump will not run on 6 volts. If it is getting 6 volts then there is a problem with the wiring. You will need to track down where the issue is and fix it.
There is no point to change a good fuse, fuses are either good or blown.
The red light on the switch could be burned out, but likely there is no power is the reason given that the pump stopped at the same time.
Just start checking for voltage and when you get to a no-voltage place, then that is where the issue begins.
Loose wires, corroded wire can be connected or touching but not conduct enough power to run the pump, dont be fooled by looks.