No brake lights - CHMSL works, though. Fuses ok.

[TequilaWarrior]

So, my wife got a driver's award the other day - 49 in a 35 with warnings for seat belt and brake lights. BRAKE LIGHTS? We just had this thing inspected (PA)!

I checked and replaced (for good measure) the underseat fuse for (BRAKE) and the underhood fuse for STP/LP with no effect. Turn signals work, hazards work - so it's not the bulbs. CHMSL works so it's not the switch. Replaced both fuses - so it's not those.

What am I missing?

 

[CaptainXL]

Doesn't the brake switch command multiple lights? Hazards don't operate the brake light, just yellow. Remove tail light housing and inspect.

 

[The_Roadie]

Turn signals work, hazards work - so it's not the bulbs.

This is the issue. Brake lights are separate filaments. They should also work even with the ignition off, for safety. It's very common for two such lamps to blow close to the same time, like headlights. People don't believe they can lose two lamps at the same time, so they go through extensive troubleshooting and skip over the most common fault.

 

[CaptainXL]

And neither the turn signal or hazard operate the red lights. Red lights are used for running and brake signal only.

 

[TequilaWarrior]

This is the issue. Brake lights are separate filaments. They should also work even with the ignition off, for safety. It's very common for two such lamps to blow close to the same time, like headlights. People don't believe they can lose two lamps at the same time, so they go through extensive troubleshooting and skip over the most common fault.

I completely skipped reading over threads at the OS. After doing some homework there it became obvious that I skipped the obvious. I'll be picking up bulbs at lunch and replacing them this evening - I'll report back once I have something to report.

 

[CaptainXL]

So I thought since he checked the fuses he must have checked the bulbs at least!

 

[The_Roadie]

Obligatory snarky reply (fair warning) because I've held back for a while:

I used to post a troubleshooting template and questionnaire before I'd get involved in an incident like this, to make sure we all had an accurate case history to go on. Too many folks either skip over the obvious and jump to a conclusion, or "forget" to mention things they did that made a simple situation worse. Not that this incident is like that at all, but it got ridiculous for a while at the OS, when new owners showed up with neglected vehicles from the used market, and the precise reason they were buying cheap trucks was they were short on experience and shallow in the pocket. A perfect storm of emergency need because they all *needed a reliable vehicle to get to work or they'd be fired, but their credit was poor/they didn't get paid enough to get a cheap used vehicle that was also reliable and good on gas*. They needed a '96 Civic, which is my DD for an 8 mile non-freeway commute and nobody's going to steal. :wootwoot:

 

[budwich]

..........
What am I missing?

A meter to actually test the circuit to see what is going on instead of just replacing things. Right now you don't know if you are chasing "lost voltage" (ie. no source of power) or dropped a ground connection or what ever.

 

[CaptainXL]

They needed a '96 Civic, which is my DD for an 8 mile non-freeway commute and nobody's going to steal. :wootwoot:

Surely you jest. I wouldn't drive a Honda simply because of the odds it might get stolen.

Honda Accord, Civic are America's most stolen cars - Autoblog

 

[TequilaWarrior]

So I thought since he checked the fuses he must have checked the bulbs at least!

Never underestimate the ability of a person to completely miss the obvious.

I made the classic mistake of thinking that both bulbs wouldn't/couldn't go out at the same time. Since both were out - "fuse" jumped to mind. Checked them. Nope, not the fuses. Didn't revisit the bulb thing (remember, they can't both go out at the same time - never happened before in the history of mankind and can't possibly be happening now).

I'm fairly accomplished working on the 360. I rewired my fan clutch(although it's acting up again). I've replaced wheel hubs, upgraded to slotted rotors, swapped out A/C head units, new water pump, new tstat, 2 coils, cleaned throttlebody, new ignition cylinder, and a eliminated slew of electrical gremlins. In other vehicles I've done complete engine swaps, rebuilt a manual trans, rebuilt a tcase, rebuilt an engine, stereo replacements to numerous and excessive to list(including a full custom dual 10's set up in a regular cab s10 that absolutely POUNDED). I did my brother's police cruiser install/integration (lightbar, wigwags, strobes, siren, pa, scanner, cb, electric shotgun lock, remote start w/ temp control, minus county provided radio) when county wouldn't pay an upfitter to do it. I've done several alarm/remote start installs (including a cellular start/monitor/page).

I just missed the bulbs. I'll replace 'em tonight and report back.

 

[CaptainXL]

I'm fairly accomplished working on the 360.

Except for electrical work. Understood. Its the hardest thing for mechanics to grasp.

 

[Mark20]

When one bulb goes the voltage gets a little higher on the others in the circuit get stressing them. Odds are if one bulb is about to head south, its mate is going to do the same even if not stressed.

 

[budwich]

I don't think so... the voltage stays the same as the bulbs are in parallel. The more likely event is that one bulb goes out, the owner never notices for an extended period of time, then the other fails eventual and then they become aware that they have no brake lights either thru "ticket" or otherwise.

 

[The_Roadie]

When one bulb goes the voltage gets a little higher on the others in the circuit get stressing them. Odds are if one bulb is about to head south, its mate is going to do the same even if not stressed.

I stake my reputation as an engineer this isn't quite the phenomenon. Factory lamps are built at the same time in a huge batch, and like lamps hanging in pairs at the parts store, are likely very similar in build parameters. The failure mechanism for incandescent lamps that get switched on an off regularly is mechanical contraction and breakage of the springy filament caused by the inrush current at turn-on. Brake lights get an identical number of these stressful events, so their lifetime is going to be very similar.

Lamps left on for a long time tend to die from tungsten evaporation and deposition on the inside of the glass.

 

[CaptainXL]

Damn good info guys.

 

[Busterbrown]

Bilateral burnouts of brake lamps I would have never assumed could happen in synchrony. But when it happened to me, diagnosing the fail point took me a bit longer as I was focused on the incorrect bulbs in the first place.

http://gmtnation.com/f23/no-brake-lights-6813/

EE's think they know everything about filament life! F'in GEEKS...

 

[TequilaWarrior]

Bulbs. Damn. Problem solved.

On a side note - I may have found a nifty trick to doubling backup light output. I'll give it a go on my Bravada soon and take pics to post (if it works).

 

[The_Roadie]

EE's think they know everything about filament life! F'in GEEKS...

EE's and Sheldon Cooper know everything about everything. It's refreshing to no longer get beat up for being a geek.

 

[Playsinsnow]

EE's ... know everything about everything.

...

Now ask me how to decorate a cake, upholster a couch, or keep a garden alive - and I'll flee.

 

[The_Roadie]

Everything that's *important*, I should have clarified. Lesser things can be delegated.

Do I contradict myself? Very well, then I contradict myself, I am large, I contain multitudes.

Walt Whitman

A foolish consistency is the hobgoblin of little minds, adored by little statesman and philosophers and divines. With consistency a great soul has simply nothing to do. He may as well concern himself with his shadow on the wall. Speak what you think now in hard words, and to-morrow speak what to-morrow thinks in hard words again, though it contradict every thing you said to-day. — 'Ah, so you shall be sure to be misunderstood.' — Is it so bad, then, to be misunderstood? Pythagoras was misunderstood, and Socrates, and Jesus, and Luther, and Copernicus, and Galileo, and Newton, and every pure and wise spirit that ever took flesh. To be great is to be misunderstood.

Ralph Waldo Emerson

 

[Playsinsnow]

See Roadie's always on it!

Sorry for the

 

[The_Roadie]

Sorry for the

Thread hijacking is what I *do*, though. I often mistreat the forums as my own private campfire story-telling session.

For some odd reason, nobody seems to report my sorry ass for it. The report would only get to me, though.

 

[Mark20]

Thread hijacking is what I *do*, though. I often mistreat the forums as my own private campfire story-telling session.

For some odd reason, nobody seems to report my sorry ass for it. The report would only get to me, though.

Its good to be the king!

 

[MichEnvoyGuy]

Are the circuit boards still a problem? On my 2002 Envoy, there was a recall IIRC on the circuit boards that screw to the brake light assembly and hold the bulbs. I had one go bad around 115k miles.

Neither bulbs had broken filaments but I replaced them anyways.. no workie still. And IIRC, the circuit board wasnt that cheap ($50 comes to mind!)