Taillights woes

[germ]

So I found out that my right taillight running light isn't working. Just the running light does not work. Turn signal, backup, and brake light, all work fine.
What could be simpler than changing a lightbulb?

Here's a part finder of the tail light:
[IMG]Tailight by dgua, on Flickr[/IMG]

This isn't very clear, but my guess is:
05: running light P21W
06: turning light PY21W
07: brake light H21W
08: reverse light 16W “921”

So I order new P21W light bulbs. Tonight I take apart the tail light:
[IMG]IMG_3155 by dgua, on Flickr[/IMG]

And replace bulb #05 (upper right in the pic).

But nothing. Running light still does not work. Then I rotated bulb #07 180 degrees, but still nothing.

What's the next step??

[Lester]

5 is outer brake light, in the separate socket.
6 is the inner brake light
7 is the turn signal
8 is reverse light
Tail/running light is an LED, not a bulb in a socket.

Check the manual, there is a good description with diagram.

[GoRomeo]

I had similiar issue with my left side taillight and remember and from the diagram I twisted the #5 bulb socket few times and thats how I got the LED running light to work. Try that see if it helps.

[Lester]

Tha manual also mentions that the outer brake light socket must be fully seated or else the LED running light may not work. It has one of those exclamation points notation, which means to pay special attention.

[GoRomeo]

Originally Posted by Lester

Tha manual also mentions that the outer brake light socket must be fully seated or else the LED running light may not work. It has one of those exclamation points notation, which means to pay special attention.

There you go. Yeah I noticed that when I replaced the bulb in that socket.

[germ]

Ok, after a bit more experimenting. Here's a better pic, that shows the location of the lightbulbs as they sit in the taillight:
[IMG]IMG_3156 by dgua, on Flickr[/IMG]

Lester got it almost right.

At first, I didn't realize there's another lamp, the "outside brake lamp" in a separate socket. That one works Ok.

All the lamp functions are indicated in the pic. Except the upper left (07 presumably), which I could not get to turn on while idling. (I didn't know we have a "brake force" lamp. Does it really work? How?)

At any rate, the LED running light still does not work. I have re-seated all the bulbs, including the one in the outer socket.

Does that mean that I have to replace the whole tail light? It's $190 online (OEM), and RockAuto has one form Hella for $130. Kind of strange that the LED would fail before the lightbulbs.

[Lester]

The brake force light is an extra light that turns on when panic stopping in North America. If you have the European light switch, then it acts as the rear fog light you can activate it with the rear fog light switch.

[Converted1]

Just went through this too with my drivers side. The LED board for the running light is usually to blame. There are some online dyi repair procedures where you have to cut into the fixture to get it out. For 120 or so I replaced it. Make sure was others have mentioned that the bulb socket furthest up and outboard is properly seated. This socket powers the led board and could be the problem.

[germ]

Converted1 Thanks for the hint.

Here's the video about board-level repair (even though it's for an E92, it looks very similar):
https://youtu.be/miNY9_GJ9aY?si=h11l386qkbmiXkT7

Also, there are several sources of a similar PCB for X3, where this problem seems to be even more common.

I am now resigned to replace the whole tail light. Any opinions on OEM vs. the one from Hella?

[Lester]

There are YouTube videos on replacing both rear taillights with black line ones. Might be time to think about that!

[GoRomeo]

Originally Posted by Lester

There are YouTube videos on replacing both rear taillights with black line ones. Might be time to think about that!
https://youtu.be/UAicie0t_1w?si=cPMPpiSoqTMIDdfP

Yeah I agree. Got a good deal on a set of used ones. I replaced mine about a month ago.

[Converted1]

I actually prefer pre LCI look and replaced the bad drivers side with the hella one from FCP. It’s identical.

[germ]

Lester Thanks for the hint, but those are $$$. At this point, I just want to spend what's necessary to keep this old car in working order, nothing more.

Converted1 Thanks, I will order the Hella one.

[germ]

Today the "brake light error" warning returned. Here's a pic:
[IMG]IMG_3164 by dgua, on Flickr[/IMG]

The error message seems misleading. The brake light works just fine. I think what this message means is, there's a problem with the "outer brake light" circuit, and that is what is preventing the LED from working.

Before I order the replacement light, I will apply 12V to the leads and see if the LED still works.

[Lester]

Maybe GoRomeo will sell you his used one!

[GoRomeo]

Originally Posted by Lester

Maybe GoRomeo will sell you his used one!

😂 Right. I do have the pair of LEDs and the pre LCI. I installed the black lines last month. Freking ended up with too many tail lights 😕😂

[germ]

Today I removed the tail light.
It is now clear how the LED running light works: it gets fed from two additional contacts at the "outer brake light" socket (the other one is at the opposite side):

[IMG]IMG_3177 by dgua, on Flickr[/IMG]

You can see the two wires (red and brown) going into a small LED board at the upper right corner here:

[IMG]IMG_3176 by dgua, on Flickr[/IMG]

I have verified that, when the running lights are turned on, the voltage at those terminals is ~14.3V. When I feed 14V to those contacts with a power supply, the LED does not turn on.

It's 100% clear now that I need a new tail light.

[Lester]

Enter GoRomeo, stage left......

[germ]

Today I installed the Hella replacement light (from Rockauto), and that fixed all problems.

The part is identical to the OEM one, except it does not have a small BMW logo where all other details are printed on the black part that is visible when the trunk is open. I am sure both parts are made in the same factory.