If your temperature light fails it will not effect the fan coming on. I was worried because my fan never came on, so in the end I installed a bypass, so I can operate the fan at anytime. K bike fans are prone to seizure so it is good to test them & make sure they rotate. Just stick your finger in and rotate the blades it can be hard to do this. My fan was seized when I got the bike, and a new fan motor was $200 Aus 16 yrs ago. So I adapted a Davies Craig car fan which is totally sealed, & run it occasionally. You can also put it on the stand and run it till the fan comes on, approximately 10min.
Regards Martin.