I have a '04 Blazer and I'm planning to install a lightbar on the inside of it right next to the rear glass, but I don't know where to wire it in to as well as where to wire it to for the DOT S.T.T. (Stop, turn, tail) modes. If anyone can tell me where I can wire it all to that would be great.

 

The easiest might be the trailer harness. All the wires you need will be there. You should be able to trace it from below the truck behind the bumper to where it enters the cabin.

 

I have a aftermarket plug wired in, would that affect anything and I can’t remember but, there are separate wires for each turn signal, right?

 

The only real concern would be if your light bar combined with a trailer lights drew too much power and could theoretically blow a fuse. Realistically, LEDs draw significantly lower power than equivalent incandescent bulbs, so you're probably fine. A bit of math to add up the total wattage of the light bar and the wattage of the lights on your trailer, compared to the fuse size on your truck would tell you if you need to beef up your wiring. If your trailer lights are LED as well, then you're almost certainly fine.

The standard 4 wire trailer harness would have separate wires for 1) left signal & brake, 2) right signal & brake, 3) marker lights, and 4) ground. I'm not sure what colours they will be in the factory harness.

 

Oh ok, I'll do the math and figure it out from there. I'm also planning on installing LED amber flashers inside by the windshield as well. do you know where a good place to wire those in?

 

I think you would be able to find the relevant circuits needed in the driver's kick panel and under the dash. It kinda depends on what circuits you need to tie into.

 

Ok thanks ill see what i can find.