Wiring help

Get test light. Turn on switch. When light comes on you have the wire you need.

 

Wire from Battery to fuseblock(AutoZone) to switch to lights.

Simple and no computer hangups

 

Seems to be small sized wires. What year and model of truck?
Newer ones are probably multiplexed and may not be able to be tapped into without reprogramming.

 

Don't tap into the wires in the back of the switch they are too small might not be able to carry the additional current, or the truck could have 'multiplex' wiring system in which case the switch does not control the light directly instead the switch simply 'tell' a module (could be the in cab module) to turn on the light and the module does it. You could tap into the wire in the back of the existing work light IF the circuit could carry the additional current, the right way to do it would be to use the existing work light 'hot' circuit to turn on a relay which in turn will turn on the additional lights.

 

Why don't you tap the lights off at the light units on the back themselves? It isn't hard to run the wiring through the sleeper.

 

I don't know about trucks but most heavy equipment comes pre-wired for accessories like extra lights. I wonder if its simply a matter of installing a fuse, relay and maybe an OEM accessory harness?