About three miles from work this morning, noticed temperature up near the red. Fan isn't working. Fuse OK. No steam (yet).
Managed to ride the last three miles by turning off the power at every traffic light and coasting as much as possible.
If manually earthing the fan doesn't work, I guess it must be the switch in the radiator. Or could it be the thermostat (which is only a couple of years old)?
Thanks all.

 

You can make a very simple test. Disassemble the switch from the radiator. Get a pot, put water and when this bubbles immerse yourself the switch. Controls with the tester, in ohm, verification if the contact is closed or opened. greetings

 

Hmm,

Grounding the fan wire to the frame (with key on) will test if fan motor and wiring are OK. Of Ok, thermo-switch in rad bad. If it doesn't work with this test, fan motor or wiring/connection bad. Get out a test light or meter and check for 12V at fan motor with key on. If yes, fan motor bad. If no voltage to fan motor, check wiring from fuse block (since you said no issue with fuse).

 

I made it home from work by missing the rushhour and riding carefully.
Fan spins OK when the rad switch is grounded, so I guess I need a new switch. I've re-wired my manual switch for the moment so I can turn the fan on and off myself.

 

done the same with mine and use the switch all the time, as soon as I hit traffic and she starts to warm I can put the fan on

 

wheelnut
As in my post 'Radiator fan switch'...
I thought it was the switch but it turned out to be a dented/punctured radiator - I was riding with NO coolant so the switch had nothing to trip it
Patched it up with J-B Weld and added K-Seal
Will see how it goes next time I ride