Another Third Brake Light Issue

[Sterling Roadster]

So after finally spending the dough on a new third brake light, 200 dollars later (import and taxes of canada) I connected to find that even the new one doesn't function. I've looked for info elsewhere but no conclusions on this one. I cleaned the connections, checked for water damage or damage of any kind and I am out of ideas. Any help is appreciated, thanks.

[Twixboy]

Uh oh, time to download WDS and start tracing the wires! Hopefully it doesn't come down to that. Did you check your fuses yet?

[Sterling Roadster]

Originally Posted by Twixboy

Uh oh, time to download WDS and start tracing the wires! Hopefully it doesn't come down to that. Did you check your fuses yet?

I will be doing that next. I know nothing about electrical so this will be a challenge for me!

[Spaceman Spiff]

Check out the wires crossing from the body into the trunk lid. Over time opening/closing the trunk damages the wires. IIRC the loom passes into the trunk lid at the bottom right corner. Here's a thread with pictures (E39 but the same concept): http://www.bimmerfest.com/forums/sho....php?p=5496188

[Sterling Roadster]

Originally Posted by Spaceman Spiff

Check out the wires crossing from the body into the trunk lid. Over time opening/closing the trunk damages the wires. IIRC the loom passes into the trunk lid at the bottom right corner. Here's a thread with pictures (E39 but the same concept): http://www.bimmerfest.com/forums/sho....php?p=5496188

Will do, a friend of mine does some electrical work so hopefully it's a small problem. I noticed also there's two plugs where the third brake light is, attached to each other but one doesn't connect to anything. Strange.

[Twixboy]

Originally Posted by Sterling Roadster

Will do, a friend of mine does some electrical work so hopefully it's a small problem. I noticed also there's two plugs where the third brake light is, attached to each other but one doesn't connect to anything. Strange.

I don't recall seeing 2 plugs when I replaced mine. Do you have a picture?

[ferrarif1]

Originally Posted by Sterling Roadster

Will do, a friend of mine does some electrical work so hopefully it's a small problem. I noticed also there's two plugs where the third brake light is, attached to each other but one doesn't connect to anything. Strange.

There are two plugs on my 06 that are identical. 3rd brake light only works when connected to the right one.

[HankDKrank]

Mine third lamp feed wire was connected to another plug and when I connected to the light it started working. As far as I could tell it had never been connected to third lamp. I think other plug provides resistance so system doesn't detect light out malfunction.

[StickMon]

Originally Posted by ferrarif1

There are two plugs on my 06 that are identical. 3rd brake light only works when connected to the right one.

^WHS

Can't substantiate that it doesn't work if plugged into the wrong one, but I wouldn't doubt it.

[Sterling Roadster]

I'll post some pics up as soon as I can, I've tried both and neither seem to work. I really hope it's not a tricky wiring issue as I already paid over $200 for this little light bar, arg!

[Sterling Roadster]

As promised a photo of the two connectors.

[Sterling Roadster]

Welp, no power going to the cables so I have to imagine the wiring is to blame here. I'll be leaving this for the spring when it's not finger numbing cold but I sure hope I didn't buy a new third brake light for nothing.

[StickMon]

The new one won't go to waste.
Yours may eventually crack, or you can sell it at a minor loss in the classifieds.

[rockstar93]

Originally Posted by Sterling Roadster

Welp, no power going to the cables so I have to imagine the wiring is to blame here. I'll be leaving this for the spring when it's not finger numbing cold but I sure hope I didn't buy a new third brake light for nothing.

Originally Posted by StickMon

The new one won't go to waste.
Yours may eventually crack, or you can sell it at a minor loss in the classifieds.

Unfortunately I can't offer any help with your issue, however if it turns out to not be the light I might be willing to take your spare off your hands if it's the red and not clear. I was looking to buy one this summer to replace my clear brake light (I think it'll better suit the Imola Red exterior) but decided against such an expensive cosmetic-only purchase, then our dollar went to crap so ordering one now is out of the question.

Here's hoping that you the new light will work, but if not I could help mitigate your repair expenses.

[Sterling Roadster]

Well just wanted to finally update this. Turns out the wiring for the third brake light was broken in a few places. My mechanic managed to stitch em' up and the original brake light works just fine. I think i'll be keeping the new one just in case though. Thanks everyone!

[StickMon]

Update here, too.
Been quite a while since I put Nyloc nuts on and tightened them roughly 1/2 way down the threaded portion.
No new cracks.

[Sterling Roadster]

Originally Posted by StickMon

Update here, too.
Been quite a while since I put Nyloc nuts on and tightened them roughly 1/2 way down the threaded portion.
No new cracks.

Hmmm, so over-tightening the inner trunk nuts cause the plastic cover of the third brake light to crack?

I have not yet had cracking, this is why I ask.

[StickMon]

Some do, some don't.
Maybe it's the California Sun, maybe it's vibration from my RE cans.
Maybe it's because my trunk lid's not straight.
I'm convinced my car had rear end damage from the P.O. that didn't make it to CarFax.

Anyhoo, my original light completely shattered. I put a new one in and within a week there were cracks along the top edge.
Went to Lowes and got some Nylocs and only put them on 1/2 way. Cracking stopped.
By design, you shouldn't be able to over tighten them. There's a positive stop when you hit the shoulder of the studs, and the springs set the force on the light housing.

[SaltyNC]

Originally Posted by StickMon

Maybe it's because my trunk lid's not straight.
I'm convinced my car had rear end damage from the P.O. that didn't make it to CarFax.

Is it off by just a mm or two? My Z4MR twin to yours is the same way -- not noticeable unless I get down at eye level with the line between the trunk and the bumper. Then, I see one side is ever so slightly higher than the other, or maybe it is the bumper that is off.

Salty

[StickMon]

The left side of my trunk lid doesn't line up with the fender. Like the lid is bent.
Maybe somebody tried to slam it with too much junk in the trunk, or maybe it was hit and they didn't get it back quite straight.
On the right side around the edge of the tail light and that little plastic trim piece the lip on the fender is folded under.
It's supposed to go over the edge of the plastic trim piece, but isn't close.

The hole for the brake light looks OK, but it would only have to be off by a couple of mm to put all the stress on the center few inches of the light.

[Steeler]

Originally Posted by StickMon

The left side of my trunk lid doesn't line up with the fender. Like the lid is bent

My trunk lid was the same.
I adjusted the hinges by loosening the bolts and realigning the lid.
Drove me nuts looking in the rear view and seeing the lid misaligned.
Wonder if all were made that way by BMW

[Sterling Roadster]

Originally Posted by StickMon

Some do, some don't.
Maybe it's the California Sun, maybe it's vibration from my RE cans.
Maybe it's because my trunk lid's not straight.
I'm convinced my car had rear end damage from the P.O. that didn't make it to CarFax.

Anyhoo, my original light completely shattered. I put a new one in and within a week there were cracks along the top edge.
Went to Lowes and got some Nylocs and only put them on 1/2 way. Cracking stopped.
By design, you shouldn't be able to over tighten them. There's a positive stop when you hit the shoulder of the studs, and the springs set the force on the light housing.

Okay if the California is causing you some trouble I have a proposition. We swap identities, I live in California and you take over my life here in Toronto. There's no snow ever, it's all a myth. Internet shake on it.