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3rd brake light not working

FL335i
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FL335i Enthusiast

FL335i

Posted
Posted

Did a LOF and some service to my truck today, figured I'd do a functional light check. The 3rd brake light is dead as a door nail. Truck is only 2 yrs old with 51,300 miles. Before I go ripping it apart, does anyone know if the thing works while parked? I even had the wife put it in Drive, still no brake light. I also need to check the owner's manual for the bulb part #. Always something. Thanks in advance.

  • Like 1
Gary13 Enthusiast

Gary13

Posted
Posted

It will and should work any time the brake pedal is pushed. Sounds like a bulb out. I believe it's a 906 bulb, but check with your local parts store for the correct lamp size. Should be an easy fix while standing in the bed!

  • Like 1
SouthernSilveradoGuy85 Senior Enthusiast

SouthernSilveradoGuy85

Posted
Posted

Manual says the brake light bulb for the 3rd is 921, more specifically 921LL. Just so you know, the manual calls it a Center High Mounted Stoplamp and not 3rd brake light. Just in case you can't find the description of 3rd brake light.

FL335i Enthusiast

FL335i

Posted
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Posted (edited)

I just checked my OM. 921 #. Turns out I had a brand-new 921 in my stash of bulbs. Leftovers from either my brother's 2000 WS6 F-body or my C4 vette, both which happen to go through a lot of 3rd brake lights. And now my '14 truck is keeping up the tradition. That bulb was still in the open box, must of been sitting in my stash for 10yrs.... Jeez, but I used it today. Just means I sit in traffic a lot.... Cost me $0 and 5 minutes. I already got it working, simple as could be. Proof of why you should do a functional bulb check at every oil change and hang on to everything.

Edited by FL335i
Colossus Senior Enthusiast

Colossus

Posted
Posted

Replace it with an Philips, GE, or Sylvania brand LED (as well as your license plate lamps) and never think anything of it again :)

fbachman Senior Enthusiast

fbachman

Posted
Posted (edited)

my '07 had tremendous 3rd brake light assembly moisture issues. At one point, I replaced the whole assembly. The rubber seal on those is tricky and easily crimped, or installed where the rubber seal "slips" inside the race and gives a poor-to-no seal.

 

In fact, the third brake light assy on my '07 caused a significant leak once that showed itself as a puddle under my drivers side floor mat. Also stained my headliner pretty bad. Worth checking often.

 

 

Not sure if the approach on the later models is any different. Hadn't had a chance to crawl up there and look.

Edited by Grumpy Aero Guy
JimCost2014 Senior Enthusiast

JimCost2014

Posted
Posted

luck was on your side, my 2008's 3rd brake stopped working. I replaced the whole light assembly and still nothing, the problem ended being the fuse slot in the main box under the hood went bad. not the whole box, just the one slot for the 3rd brake light fuse, had to replace the whole unit for $550.00.

  • 6 years later...
HarrisonA New Member

HarrisonA

Posted
Posted

2016 Chevy Silverado 3rd brake light not working. Tested fuses, bulbs, all of it. We’re down to tracing and checking relays. No power. New bulbs but no power there or the license plate lights either. Ideas? 

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