My dad just recently bought 4 lights off Ebay to install in his 2004 Chevy Express box van. The lights are going in the "box" so I was just going to tap into the existing light that's already in there. My question is what all do I need to do so? Relays? Can the stock wiring handle the load of the 4 lights? They're double bulb lights so it's a total of 8 bulbs.

 

Personally I'd tun it on its own harness like make your own. this way you can easily find a problem if one should arise. Including a relay and a fuse's. then mount a switch where desired

 

What size bulbs. What light are you busting into. what is the end product you wish to see.

Just from the superficial level I would say that the stock wiring cannot handle the addition of 8 bulbs of any size but hopefully the fuse will tell you that. ERGO, you will have to run new wire, ergo new relay and fuses. but then again what size lights

 

I'm not sure of the bulb size. My end product that I wish to see is all the lights being turned on with the factory switch. They're a small bulb. It looks the same as the dome light bulb in my truck.

 

then I say maybe. Small bulbs like the ones in ranger corners/dome lights are ok for seires installation only if the source your busting into is strong enough to power all of them. if you try to put 8 small lights; lighted from one small light...no bueno...but 8 small lights run off same circuit as one normal/big light then yeah it will handle the load.

figure out the amperage/voltage of the existing bulb in the box. then, since the new bulbs will be in series, find out the amperage of just 1 of the new bulbs, multiply it by 8 and if its less then your good to go with the stock wiring.

 

Separate Circuit w/relay, fused power wire and On-Dash Switch.
Leave the OEM Interior Light alone and add the new circuit so the lights can be used as needed.
maybe have two switches, Dash one always on and mounted out of the way and another one by the box door; that way if you need light you turn them on at the door.
One switch by the door will do too.