Glad it all worked out Guys:

Jonny / Glyn:

Maybe it was just a tight fit on my Bro's bike or a poor fit between threads, in any event I filed the outer circ of the washer quite a bit and then wrapped it in PTFE tape. Overkill perhaps but it worked a treat.

Derek:
Welcome back mate, youve been missed!
I'd never dream of taking any sort of credit for your sensor work or external fuel filter mod or headlight suggestions or......

bl00dy 'eck time to stop :lol:

Cheers - Frank

I googled a # Derek had posted for this switch, and came up with a few hits for BMW's, Volkswagon, Citreon, etc.
Found it at the auto parts online for $16.76 US, ordered a couple for myself for my 99 ST2. The fan seems to be coming on later than I like. New +/- errror was listed at 3.4'c at 100'c, fiqure 2 sensors with some age on them maybe 10'c or more possible error. I'll change them and feel better, hoefully run cooler.
My fan isn't going on until 221'f, but the bike is running between 155-180'f [so far, just got it going 450 mi. ago]and I live in the desert.
0-280-130-026 Bosch not sure if this is the long or the short one.

what if the fan goes round but not as fast as it does when you put 12 v direct to it ?

Probably a dodgy relay, but possibly the connections to the relay or to the fan.

it starts and eventually gets to a speed where you cant see the blades but previously you could hear it when sat on the bike with the engine running and helmet on. Now you cant hear it at all and the temp keeps on rising albeit not as fast as when it didnt work at all.

The only things between the fan and the battery are the relay, 2 fuses and various connections. The 7.5A fuse is under the seat alongside fuel pump and ECU fuses and they are all supplied directly from the main fuse in the fuse box (Fuse 1 = 30A). I think it is reasonable to assume that the feed as far as the fuses is OK or the fuel pump and ECU would also be running at reduced voltage. So the most likely reason is a bad connection at the fuse, check the blades for corrosion, a duff relay, but you said you have repaced it, corrosion in the relay socket, or corrosion in the fan connector terminals.

I suppose it's also possible that the fan bearings are full of crud. Does it spin easily by hand?

I fitted one of these, its a straight swop and it cured my misfire.:)