I put the TFS600 fan switch into the bike and then wired it through a 30 amp relay. When you go the relay route you have to bypass all the old wiring for the fan/thermo switch combination. Take the main power lead from the battery through a 10 amp fuse. You can put a bigger fuse in but seeing as fan is only supposed to draw max of 4 amps, a 10 amp should work fine.
You can use the blue wire that goes to the fan for your 1 amp switched circuit to the thermo switch side of the relay. Just unplug the fan & use a connector and run it through a 1 amp fuse to the relay. That way the fan won't come on with key off. You'll also have to come up with a couple of ground wires, one each for thermo switch & fan.
Now for the results. I'm running a Stant 180 degree thermostat that is designed for Honda cars. ( This was the same thermostat for both the Geo & Honda car thermo switch project. ) With the NFS600 switch when I started the bike & let it warm up the fan will now come on at a point at about two or three needle widths into the operating temp range of the gauge. When the fan comes on it drops the gauge down to about 1 needle width into the temp range. I let the fan cycle off and on a few times then shut the bike off. It stayed in this temp range throughout. I watched the overflow tank to see how much the antifreeze expanded as the bike came to operating temp. The expansion was half of what it was with the Geo thermo switch. ( In otherwords engine didn't get as hot. )
1. There is a lot of messing around once you go away from the stock set up. I think if you like to tinker than doing what I did is fine. Like most things I don't know that it is better, however the bike does run cooler than it did with the old thermostat & Honda GL1000 thermo switch, also with new thermostat & Geo switch. I never liked having the engine run in the upper/top of the operating temp range of the gauge when in parade mode or around town. I'm pretty sure the fan will run more with this set up but the operating temp should stay in a narrower range.
2. If you don't like to tinker, put the orginal thermo switch back in. I couldn't find one up here so that's why I did what I did.
3. On a cost basis both set ups end up costing about the same, by the time you buy all the pieces for the aftermarket setup.
I will post another update once I can ride outside in the real world. It was minus -25 C this morning. As a sidebar note the TFS600 fan switch is the same one that is in my 2006 Honda CRV. So should work fine in the bike.
Currently own: Restored 1977 Goldwing
Current project: Restoring 78 CB750F
Previous bikes: XJ650, GS550, XT500, 77 Goldwing, and a few others