If it's a four pin switch then that means you have dual speed fans or individual control of each fan.

It may be you have a partially blocked rad which I would think is unlikely as you would notice it elsewhere, thus the switch not working as the coolant temperature is never reaching the switch, IF you have a rad switch, i.e. it's not located in the thermistat housing as all models differed, other than that, as said, the only other thing can be a bad switch.

It should only be until you get it working properly, having fans on a switch is never a good idea, say you forget to switch them on etc, plus you cannot activate them at the correct temperature like the switch. It's an automated system for a reason!

Your wiring dosen't make sense, the switch just completes the GROUND circuit for the relay, so you shoulden't have to be running lives anywhere, so have you wired direct to the switch plug, or the fan connector(s)?

Martin