So I just got a cap for my 04. What is the easiest way to tap into the brake light system for the 3rd brake light? Not sure if you can tap off the tail lights with those goofy tail light circuit boards they put in these trucks.

Obviously tapping off the trailer wiring won't work because there is no "brake light" wire. Just left/right turn/brake which would make it blink with the turn signals.

I'm sure I can run a wire from the cab 3rd brake light but that seems like it's a lot of work. There should be something easier... shouldn't there be?

Thanks in advance,
Joe

 

mine is just a LED row of bulbs and because of its low draw its just tied in off the left brake light.

 

Do you remember what wire it was?

 

My cap dealer spliced the trailer harness and installed a quick disconnect in case I wanted to pull tje cap off my truck and he ran it thru the left rear stake pocket....I believe he tapped the brake light wire off the taillight

 

Yeah, I would just tap off of a brake light in one of your tails, as soon as you figure out which wire it is. Just make sure all your connections are solid and free from corrosion in the future. An easy disconnect is a great idea also!

 

I was just looking into the same thing for my '08. The correct wire at the left rear tail/brake lamp is white w/green stripe. If you don't want the 3rd brake light to flash when the turn signals are used then you must purchase a "logic box" for $12 or so from a truck accessory/truck cap dealer. They might be available at an auto parts store possibly, I know they have similar devices for some trailer wiring applications.

 

2008 Dodge ram - There is wire behind the spare tire, slightly to the left, look up at the harness, white with a brown/tan stripe that is capped and outside the harness. It is the 3rd brake lamp wire. Wire it up and no worries about the 3rd brake lamp blinking if turn signal is on.

I too was trying to find a solution, looked into logic module, run wire from front,etc and found the wire eventually.

Thanks
Dennis

 

My 3rd brake light on the camper shell will work when the brake is presed BUT it reamins on at a very dim status when the pedal is not pressed.
Checked voltage on wiring when brake pedal is not pressed and aronf 9 volts remain on this wire.
Am I using the correct wire or could that be a problem in the barke light switch?

 

Sounds like your wire may be tied into a turn signal wire.

To start, I would make sure that it is hooked up to the CHMBL (Center Hight Mount Brake Light) Wire (brown/tan stripe) that Dennis mentioned above.

 

Mistake, see next post.