91 CBR1000F radiator fan
 

What do I need to be checking if my coolant fan wont kick on?

Hi, first thing to check are the electrical connectors to fan, sender unit etc. Just make sure they are all connected properly with no loose wires.

There is a thing screwed into the front of the bottom left side of the rad with a wire attached, that's the sender unit, when the water gets hot enough that wire is grounded through the rad and the fan should start. Turn the bike on, unplug the wire and touch it to the frame somewhere, the fan should start.

If it starts then you might have a bad sender unit or a bad earth between the rad and the frame, All the radiator mounts are rubber, so there has to be a wire somewhere attaching to a bolt grounding the rad.

If it doesn't work then check the + side, I think there is a dedicated fuse and even a dedicated power line running from the stock ignition switch?

Tim.