And a Happy New Year to you also! In response to the fan question, you'll need to identify/verify how the circuit operates but many that use the sensor simply control the ground side of the circuit. As a test, turn the keyswitch to on and then touch the wire that goes to the sensor to a metal part of the motor. If the fan starts, then you simply need to add a wire through a switch that can open/close the ground circuit.

If it doesn't start, then you'll need to identify the power wires and test them for voltage, if none is found then you'll need to send power through a switch to open / close the power circuit.

I'll bet yours is the first scenario. Do a couple investigative tests and let us know the results. There are a couple really good guys on here that play with electricity and are very helpful.