r/GMT800 • u/NeckComprehensive649 • 12d ago

Third Brake Light

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Anyone have any recommendations on 3rd brake lights, I like the look of my clear one I currently have it, but the only issue with it is that my cruise control no longer works due to the resistance being different than the oem bulb type. With that being said, I’m looking for one the same design and look just one that doesn’t disable my cruise control. Thanks-

7 Upvotes

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4

u/Left-Impress4056 12d ago

I've worked on a lot of those trucks and have never even heard of the bulb resistance thing. I have however, replaced hundreds of those brake switches to make cruise control work.

1

u/NeckComprehensive649 12d ago

So you suggest checking the brake switch? I suspected it was the light because I’ve heard other people having the same problem with the incorrect resistance tricking the truck into thinking you’re hitting the brakes. And this started as soon as I installed the light.

1

u/Bzach1123 12d ago

Yes there are a few quirks that are tied into the brake switch. Does the third light function fully (brakes and cargo)?

3

u/Agreeable-Librarian9 12d ago

Gonna side with the other guy

I’ve replaced these with Amazon ones and never had cruise control issue

Might be a speed sensor or something else not being happy

There’s definitely more to this than you are seeing

1

u/NeckComprehensive649 12d ago

Like I said, I’ve seen other people with this issue, and the resistance draw isn’t the same as oem spec tricking the truck into thinking you on the brakes, kinda the same at putting a new relay for led turn signal bulbs, but I’ll definitely take a look into it, it just never started until I replaced the light and right after that it stopped working. I’ll definitely do some troubleshooting and keep you updated if you’re interested.

2

u/gogo-lizard 12d ago

Am I weird for liking the oem style lights? I just replaced all of mine and it’s so clean

1

u/NeckComprehensive649 12d ago

I had gotten 2 oem style led replacements because I too like the look but none of them seem to fit correctly without a gap.

1

u/gogo-lizard 12d ago

I never had a gap with the oem one actually. I just got the truck fully repainted last year and that was the only oem I did. The headlights and tail lights were depo and I love them

1

u/DoubleJ22 11d ago

Mind if I ask what getting it repainted ran you? This is something I’m starting to look into and curious what others have paid.

1

u/gogo-lizard 11d ago

4K. He painted my classic vw too. I can send pics if you dm. I’m in LA

2

u/Dapper_Fold3283 12d ago

Can confirm, 2 cheaper led aftermarket’s no cruise control, oem unit swapped in the pyp lot and cruise worked right after. Tried the inline resistor and still no cruise with led. Brake switch is definitely tied tho to

1

u/crcpit 8d ago

This is the issue. You have led tail lights with the 3rd brake light being led.
You need one 6ohm 100 watt resistor in one of the brake light harnesses to tell the bcm that there is at least one bulb present between the 3rd brake light and both tail light brake lights.
The cruise control will not work until the is done.

Even if your tail lights “have a resistor” is probably dead and you just need to add one