Not sure if it's my brake light switch that's bad or just the wiring. This is on my s5 TII RHD swapped car. When I did the swap, I had to make the USDM body harness fit the JDM harness. The wires colors are not the same, and there's not even the same amount of wires. I am no wiring guru either. I managed to get everything working but the brake lights. After much testing, I just could not find the correct wire. Either that, or the brake light switch was bad and no amount of testing wires would let me know which wire was correct.



So, how do I test if the switch is bad?



And if the switch is good, and I just did not wire it... then I do not want to tear out the carpet again and go through all the painful wire tracing again. I figured it would be easier to just wire it completely separate from the harness.But I am unsure on how to go about this. Anyone want to give me a few how-to tips on how to wire in the brake switch completely separate from the harness. Basically run my own wires from the switch to the lights. Seems super simple in my head.But it's always good to ask first before I go out and waste 2-3 hours hooking up stuff until I figure it out...



Thanks in advance...

OK, did a little google search and found a how-to on how to test the switch. This is how I did it.



I put the positive lead from the tester to one of the prongs on the switch, with the other lead from the tester grounded.The test light lit up , This make that wire the power wire for the brake switch. I then moved the positive lead to the other wire on the switch. The test light did not come on making that the "signal wire", With the leads in the same position I depressed the brake pedal. The test light illuminated proving the brake switch is operating properly. This is exactly how a properly wired and functional brake switch is supposed work.



So why do I not have brake lights???

Your headlight switch could be bad or you dont have it wired right

Brake lights have nothing to do with the headlamp switch. However, some vehicles do pass the wiring throughout the combination switch. I'd have to look at the schematic later tonight. What year is it?

Knew a guy who went through a simmilar problem it was his headlight switch

Just looked through the schematic and it goes from battery, btn fuse (60a), Stoplight fuse (20a), stoplight switch, then to all the brake lights. The harness for the stoplight switch should be inspected to though because it moves with the brake pedal. After time dry rots the insulation plus the constant movement, I've seen the wires become exposed and either break or short out. Best of luck man

Thanks for doing that! That should help me get to the bottom of my problem...

No problem. I spent 3 days at my shop trying to figure out why the brake lights only came on intermittently on a 96 k1500. Turns out harness was broken above the steering column. Had to pull the entire column out to get to it. Not fun and I wouldn't wish that nightmare on anyone lol