From time to time, I'd like to know if my puller fan is on. With road noise, and engine noise, I can't always tell. I didn't want to make a big deal about putting a light somewhere that would bother me, and I didn't want to punch a hole in the dash, and I wanted something that I could see even in the bright sunlight, but I wanted to be able see it out of the corner of my eye without having to actually look at it. But I also wanted to be able to disable it easily. Basically I wanted something that was easily seen by the driver, but only if you're looking for it, but that wouldn't be noticed any other time, and that could be turned on and off easily. This little blue light latching push button switch mounts over in the bottom corner of the dash so it's over in a pitch black area of the door jamb. The driver can see it easily without having to look at it. It lights up blue when the puller fan comes on and goes out when the puller fan turns off. To disable the light, just turn it off by pushing it. And if you want to remove it entirely, the bracket is just held on by the dash screw. It's wired directly to the 12v+ output of the puller fan relay and protected by a 2 amp fast blow fuse. Wired this way if you saw your temperatures climbing higher than normal and your blue light is not on (because either the fan relay failed or the thermostatic switch failed), but should be, you can throw the pushers on and limp home without overheating. Not a huge project, but a fun one.
