Can anyone tell me what this switch might be? I just bought this 07 fat boy, and for the life of me, I can’t find anything that changes or comes on or anything when flipping this switch. I did notice an aftermarket relay/fuse holder under the seat when I installed my tuner. The wires on the switch seem to go behind the headlight.

 

perhaps the previous owner has some aux lighting

 

There is a lot of extra junk connected to the positive battery post...

You are going to have to trace the wires from the switch and find what they connect to...

 

First thing I'm seeing is the switch goes to a relay that provides battery power to something, as previously stated you'll have to trace the wires to find out what that something is. Good thing is that wire should be outside of the main harness so it should be easier to trace.

 

While you are in there, move the battery cables to be the first thing touching the battery post - not the tender harness.

 

It was in fact a flashing module for the headlight during daylight