wiring up a light switch

I don't know if I can help you, I don't know what year, make model truck it is. You say that all the wires are labled? What to those labels say? Is it 1 label for all the wires going to the switch that says spare? Or is each wire labled with a number? Or what? Many on many trucks, you just need to find the correct accessory wire to power the accessory and add the correct fuse. Some are a little more involved.

 

Just tie into a hot FUSED power source. Get a test light and start poking around. Sometimes I'll run a hot right from the battery or just find an open in the fuse panel. Just make sure you have an in line fuse right at the power source. In my youth a almost burned up my 79 Ford truck twice and a 4440 jd before learning that lesson

 

Not sure how IH does it, but usually on a KW there is already power to the aux/spare switches. If that's the case all you need to do is run a power and ground wire from the switch to the lights.

 

What kind of truck is this?