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Greg A
Greg A, Master Troubleshooter
Category: Chevy
Satisfied Customers: 7950
Experience:  Working with Electronics & Cars for 25+ Years
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how to wire a brake light for a truck topper to the truck ...

Customer Question

how to wire a brake light for a truck topper to the truck brake lights,
Submitted: 8 years ago.
Category: Chevy
Expert:  Greg A replied 8 years ago.

HiCustomer Thank you for asking your question on Just Answer.

Can you tell us the Year, Make, and Model of your truck?


Customer: replied 8 years ago.
Reply to Greg A's Post: 1997 S-10.

I had the brake light on the topper wired to the wiring harness on the truck (that would connect to a trailer) and it worked fine when i applied the brake, however it also came on with the right directional signal
Expert:  Greg A replied 8 years ago.

Hi Monty,

You could tap into the wiring for the center stop light, but according to my schematics, that is where the trailer wiring is supposed to tap in anyway.

What color wire did you attach the power wire for that light to?


Customer: replied 8 years ago.
Reply to Greg A's Post: the topper brake light has a red and black wire

and the wire harness has a four pin connection

( three female and one male connection ) a white, brown yellow and green.

I connected the topper red wire to the green and the topper black to the white which was the only male connection and thinking it was a ground.

like I said it worked fine but also came on with the right signal

thank you
Expert:  Greg A replied 8 years ago.

Hi again,

OK. Give me a couple of minutes and I will see what I can find.

What appears to be the case (so far) is that the trailer wiring you have is only for the turn signals, running lights, and ground. We will have to find an independent brake signal somewhere.


Expert:  Greg A replied 8 years ago.

Hi Monty,

I just wanted to keep you up to date on what I have found.

Dark Green - (circuit 1619) TRR TRN (fuse in under hood) - Right Park & Turn Signal
Yellow - (1618) TRL TRN - Left Park & Turn Signal
White - ???
Brown - (2109) - TRL PRK - Parking Lamps

What should be somewhere, close by, is a light blue wire, which would be used for the stop lamp. You may be able to follow the trailer wires back under the chassis and find this light blue wire. That would be where you would have to connect the topper light.

If you can not find that wire close by, you have a choice of:

1) Running a long wire into the underhood fuse block area, and tap into the fuse block where you should have a fuse socket (and possibly a fuse) labeled TRLCHMSL (right next to the one I have highlighted in the diagram below).


2) Getting one of those "center mount lights" that they have at the auto parts store that comes with a little electronics box that will prevent the center light that you are installing from flashing when either turn signal is used.


I hope this helps. Please let me know if you have more questions.

Take Care, Greg A.