I kept a plug and socket in the circuit, similar to the '2 Way 6.3mm Multi-Connector DJ7021-6.3-11 Terminal Block Plug Electrical Socket' referred to in the above link, but I soldered a length of cable to the cables from the fan, this allowed me to raise the position of the connector so it was away from any water that gets thrown up from the road. The original position just resulted in the connection getting drowned with water, resulting corrosion and bad connection. If your fan is controlled from the ECU (slow and fast relays) you can test them using the Forscan software (using a PC with a usb/OBD link)
