Hello everybody.

I just bought a 2005 suburban LS
And the brake light won't come on
Tails lights work , as well as head lights ,fog lights ,turn signals and hazards.
I checked all fuses related to brakes, I changed brake light switch and tested it. 14v @ constant, 14v@ switch when brakes depressed. I have no clue what else to do!
Please help!

 

Welcome to the forum.

I assume you checked the bulbs dual filaments and for the presence of voltage at the socket w/ the brakes applied.

Not sure if this is applicable to your truck but most circuits are activated by a switch to ground. If this is true, then you shouldn't have any voltage present at the switch w/ the brakes applied. Did you check the new switch w/ an ohmmeter to make sure the contacts are closing?

 

Check your turn signal switch. GM ran the brake lights through the switch to cancel the brake light when you activate the turn signal. Now I know somewhere in the 2000's they separated these two functions:

simple tests
3rd brake light still work and you have 2057 bulbs for turn/brake light function: suspect the turn signal switch
you have separate bulbs for each: suspect the converter box that adds the brake/turn signal back together for trailer towing or a poor connection within this wiring

use to be white/green/yellow for the single bulb (turn/brake) setup. white from the brake light switch into the turn signal switch. green and yellow for the right and left turn signals

hope this helps as I stepped out of the automotive repair industry during the mid 90's :-)

 

Had same problem with my 2000 K2500. Turn signals, tail lights and hazard all worked, as did thee upper brake light, but no lights on the rear. Brake light fuse on the side of the dash was fine, although I swapped it out anyway just to be sure. Figured for sure it was the switch on the brake pedal, so I changed it (not a job I'd care to do again in the near future) and STILL not brake lights. I read about the turn signal switch issue and was mentally preparing for that task. I decided to recheck the brake relay under the hood and as I was snooping around the fuse box, I noticed a 30 amp fuse marked "stop/hazard" on the diagram in the cover. Just for the heck of it, I pulled it out and sure enough, it was blown. The hazard still worked however. Swapped another 30 amp fuse in there and presto, brake lights. I thought the only fuse for the brakes was the 10 amp one inside. Learn something everyday.

 

GregS,


Thanks for posting this info. I had the same problem and I went through the same exact steps as you right to the turn signal switch. Read your post and I figured I would check it out. Mine ended up being the same 30 amp fuse. Still not sure why my hazard lights worked the whole time, but I guarantee that this particular fuse will be one of the first things I check if I run into this problem again. Now if I could only get back the hours that I lost chasing my tail.