No brake lights, except for 3rd

[JarrodH]

Solved...kind of.

So, I've searched on here to try to find an answer, but can't seem to find it.

Today a buddy from work called me while driving behind me to tell me my taillights were out, but the 3rd brake light on the tailgate was working.

Here's what I've checked so far:
- Bulbs are fine; they light up when headlights are on
- All fuses are fine
- I replaced my multifunction assembly (turn signal) a few months back with a brand new one
- As I said, 3rd taillight illuminates fine
- I pulled the connection to the BPP and had 12v from pin5 to ground
- Used a wire to jump pin5 and pin4 on BPP, and still only the 3rd brake light came on.

What else can I check?
I followed this post: http://www.explorerforum.com/forums/showpost.php?p=2262658&postcount=8
But didn't understand where the connector in the last step is.

I can try a new BPP switch, but if it were bad, wouldn't that mean the 3rd light wouldn't light up either?!

 

[jremington59]

Is there a three bulb set up in them? The running light bulb would be diffrent than the brake light bulb. Do the reverse lights work?

 

[JarrodH]

Is there a three bulb set up in them? The running light bulb would be diffrent than the brake light bulb. Do the reverse lights work?

Blinker is one, brakes/running light is another, and reverse lights are a third bulb. The brake light bulbs only have two contacts, so it's not a two-filament bulb.

 

[RomeovilleIL]

First and foremost I would check to see if you have a trailer harness attached. It's not uncommon for crud to build up in the plug and short out your current. If you have one, unplug it from behind the left taillight housing and see if the situation is corrected.

After that, best advice is take your volt meter or test light and start investigating at the rear of the truck since we know voltage is getting to the top bar. I believe the top light and l/r brake lights split power in the loom at the connector plug in the jack storage area.

A ground issue is not likely as the parking lamps and brake tights share the same grounds. Still both of the sockets have might have deteriorated so pull the bulbs and check for voltage there anyway just to rule that out.

Since the top still works, if there is no voltage at the sockets a short or break is somewhere in the rear of the truck between that set of plugs and the lights themselves. Thankfully that area is not difficult to access and you are only dealing with a couple feet of wire.

 

[RomeovilleIL]

Blinker is one, brakes/running light is another, and reverse lights are a third bulb. The brake light bulbs only have two contacts, so it's not a two-filament bulb.

???

You should be running the 3157 brake light bulb. It has 4 contacts and dual filaments. If you got a single filament bulbs in there your answer is change to the correct bulbs.

 

[jremington59]

When you put it in reverse do the reverse lights come on? Just because you have running lights doesn't mean the brake bulb isn't bad. The best thing to do is have someone step on the brake and see if you have power to the socket. You said they come on when the headlights on so I assume it's the brake light your having problem with?

Blinker is one, brakes/running light is another, and reverse lights are a third bulb. The brake light bulbs only have two contacts, so it's not a two-filament bulb.

 

[JarrodH]

???

You should be running the 3157 brake light bulb. It has 4 contacts and dual filaments. If you got a single filament bulbs in there your answer is change to the correct bulbs.

You are correct, it was the 3157 bulb, shame for me trying to figure out the problem at night.

And it turns out, it was the seating of the bulbs that was the issue... and I'm not sure how in the hell they both got dislodged in such a way that the running light filament would work, and the brake one wouldn't. One of the times I was testing, I went to pull out the bulb while I had a bottle wedged to hold the brake pedal down, and eureka, the bulb went on.

So, somehow, both of my 3157 bulbs seated themselves too far INTO the socket. How the hell that happened with both, I have no idea. One did have a slightly melted contact, so I did replace the bulbs anyway. But for the life of me, I can't think of how two bulbs would lodge themselves farther into a socket, on their own, at the same time.

 

[budwich]

putting them in wrong "at night" by the same person...

 

[JarrodH]

putting them in wrong "at night" by the same person...

I never even touched the passenger side one until today though. Meh, whatever, they work now, less likely I'll get rear-ended.

 

[00meangreenXLT]

You are correct, it was the 3157 bulb, shame for me trying to figure out the problem at night.

And it turns out, it was the seating of the bulbs that was the issue... and I'm not sure how in the hell they both got dislodged in such a way that the running light filament would work, and the brake one wouldn't. One of the times I was testing, I went to pull out the bulb while I had a bottle wedged to hold the brake pedal down, and eureka, the bulb went on.

So, somehow, both of my 3157 bulbs seated themselves too far INTO the socket. How the hell that happened with both, I have no idea. One did have a slightly melted contact, so I did replace the bulbs anyway. But for the life of me, I can't think of how two bulbs would lodge themselves farther into a socket, on their own, at the same time.

Those bulbs get really really hot, that's probably what caused your contact problems because they get hot enough to warp the plastic socket, and make the metal contacts become so brittle and sensitive that the bulb will have to be seated just right to work. I've seen the damage that can happen to these things over time, my mom used to have a 2004 Pontiac Montana that used the front turn signal 3157 bulbs as daytime running lights, and because they were on anytime the car was running, the sockets melted to the point where the bulbs were permanently melted in and of course no longer worked, and it even melted part of the corner light housing on one of them.