[07lilredwagon]

heres a good one...

I have a tail light out...the running light in the hatch of my e91.

I am getting power to both tail lights.

both tail lights (left and right) are getting 8.5v or thereabouts. (seems low)

but only the DS light is working.

I have switched bulbs. no luck on the right side.

I have switched housings, same issue.

I am getting voltage at the housings!....when I plug the bulb in on the right side....nothing.

HOW CAN THIS BE? GETTING VOLTAGE AT THE PLUG, THROUGH THE HOUSING FIXTURE, AT THE PLUG RECEPTACLE.

WHY IS MY BULB NOT WORKING????

it was intermittent for a while and would come and go. now it seems to be out for good.

I have heard that BMWs can sense overall voltage for the lighting circuit and if there is something out of place, it will tell you...is this how?....too much resistance somewhere?

should I check all the other lights for corrosion or something?


any help is much appreciated!

thanks

JP

[N52bigblock]

Broken wiring in the rear hatch is quite common. Basically the wires break from the flexing when opening the trunk. See the photos in this post. https://www.e90post.com/forums/showthread.php?t=683942

[07lilredwagon]

Originally Posted by neilj35

Broken wiring in the rear hatch is quite common. Basically the wires break from the flexing when opening the trunk. See the photos in this post. https://www.e90post.com/forums/showthread.php?t=683942

yes, I have seen that issue before...but Im getting power to the socket, plug, housing....

any other ideas?

thanks

JP

[gbalthrop]

Originally Posted by 07lilredwagon

...I have a tail light out...the running light in the hatch of my e91... both tail lights (left and right) are getting 8.5v or thereabouts. (seems low) [TOO low to light the bulbs -- what are you contacting with your black probe to read the voltage -- metal in the hatch, the bulb socket?] but only the DS light is working. [NOT sure what you mean by "DS light" -- you mean Driver Side (Left) inboard tail light on the hatch, and Right inboard light does NOT light at all?]

Originally Posted by neilj35

Broken wiring in the rear hatch is quite common. Basically the wires break from the flexing when opening the trunk. See the photos in this post. https://www.e90post.com/forums/showthread.php?t=683942

Originally Posted by 07lilredwagon

yes, I have seen that issue before...but Im getting power to the socket, plug, housing...any other ideas?

As I'm sure you know when you stop to think about it, a light "circuit" requires not only 12V+ from the power supply wire, BUT ALSO a good ground, without too much Resistance, to have the current flow back to the Battery via the Chassis and Battery Ground Cable, attached to the chassis.

As Neil states, wires in the bundle at the hinge point, within the black Sheath/ Gaiter/ Grommet have a nasty habit of flexing (instead of rotating) at the hinge point until they break. If a significant number of wire strands in one of the Brown Ground wires has broken, the result is the SAME as if the 12V+ Power Supply wire had broken in that fashion. The fact that the failure was progressive, suggests such a breaking of the wire strands, more over time, until all, or virtually all, continuity was lost.

Suggested Test: per the comment made to your first post, WHERE you placed the Black meter Ground Probe should determine if you have a bad ground at the bulb socket. If you put the Red probe on the 12V+ power supply wire or part of bulb socket to which it connects, and you put the Black Probe on the Brown (Chassis Ground) wire at the socket, and you get ~ 8V, NEXT put the Black Probe on the Body/ Chassis ground (as opposed to the tailgate) and if your meter now reads ~ 12V, the groundwire to the bulb socket/ tailgate has an issue. Also, if the ground is the issue, you will see similar issues with the backup lights, and probably inner brake light (if installed/ active).

Of course, you can also simply test resistance between the bulb socket ground and the chassis (NOT tailgate). My bet would be that both Right & Left have higher resistance than they should, with the Right being higher Resistance (Ohms) than LEFT, explaining why Left lights & Right does NOT. Here is the TIS circuit diagram for your tailgate (inboard) tail lights, power supply from the FRM (R Inner light unit is E81 and Left is E80). There are three (3) 12V+ wires from the FRM to each light unit, and ONE ground (Brown wire) shown in later-linked schematic:
https://www.newtis.info/tisv2/a/en/e...module/hiaDKxH

So as NOT to make this even MORE confusing, the discussion below ONLY relates to the wiring of RIGHT Inner light unit on the tailgate, as that is the one MOST problematic.

For instance, the 12V+ wires go to pins # 1, 3 & 4 of Connector X328 at the Right Inner light unit on the tailgate, and the Brown Ground wire goes to Pin #2 of that Connector X328. Here is the Ground schematic for the Right Inner light unit (E81). Note that that Pin #2 is connected to Chassis Ground Connector X498 behind the RR wheel well, under the trim pad, per the Installation location, 2nd link:
https://www.newtis.info/tisv2/a/en/e...8-x498/lqX8DgL
https://www.newtis.info/tisv2/a/en/e...200703/SIvBd98

Here is "Connector View" of the 4-pin connector, X328, at the Right Inner light unit on the tailgate. Once again, the Ground/ Brown wire is Pin #2:
https://www.newtis.info/tisv2/a/en/e...-x328/CTLOLnQW

NOW, to compare the Ground Circuit on the LEFT Inner light unit. Here is the Ground circuit for E80 (LEFT Inner unit):
https://www.newtis.info/tisv2/a/en/e...-x1256/m4AP5lR

Note that the Brown wire runs from Pin #3 of X329 connector to a Common Splice or Connector X1256 which is located on the inner surface of the tailgate per this Installation Location:
https://www.newtis.info/tisv2/a/en/e...-x1256/Rk9UtGt

There is another Brown wire, DIFFERENT from that for the Right light unit, that runs to the same Chassis Ground Point, X498. So if your Right Inner light unit is NOT lighting, but your Left is, you should see Less resistance on this wire going from Pin #3 of X329 (Left Light unit) than you do on the corresponding Pin #2 of X328 where the bulb does NOT light.

Confused yet??? -- it's late enough I'm boggled by now. Hope there aren't too many errors in the above. Please let us know what you find.

George

[PichaDis11]

Pull the codes within your FRM. The FRM has the option to disable a leg of a lighting circuit if it had detected issues for some period of time. I believe I read that period is 52 ignition starts. Only a hunch as my taillights were shut off because of corrosion on the contact points of the housing and bulbs. I cleaned them up and was able to reset the short circuit counter using tool32 and all is well.

This is just a hunch as I am not sure the module still delivers power to a circuit it disabled.
Cold tests are done to all exterior lights via short bursts of voltages with FRM measuring those. This is done every time the engine is started.

[E90SDGUY]

If you figure the answer to this please let me know. I have exactly the same issues. I've checked all the wires, nothing is frayed or broken.

[07lilredwagon]

YOU GUYS NAILED IT ON THE HEAD!

I began testing the feed side of the tail lights, getting power but only 8.5 -9v at the bulbs...I knew something was up.

so I began testing the ground side of things and found the issues.

I had no ground continuity on the right tail light due to broken ground wires. but where they?....you guessed it....in the gaitor/wiring loom going from the top of the body roof to the hatch wiring. I had several broken wires, many more broken wire casings and all but 7 wires compromised beyond simple repair!

arrrggghhhh!....so one by one...inch by inch, I replaced each section of wire so I would have fresh new wire at the bend in the loom. this was complicated as I staggered the crimp/heat shrink/weather proof connectors along the length of the loom away from the bend. I did this so they will all hopefully fit back in place. that will be tomorrows project.

I had to take all the plastic trim off the surround for the hatch and from the rear opening in the body just so I could get to the wiring and for diagnostics. it took time!

I accessed the wiring just under the roof panel on the right side under the gaitor...I have it pried open with a roll of paper towels and that is where I am spicing the wiring inside the car.

This also explains why I had a battery drain and voltage drop readings. the casings on the wires were so compromised Im sure I was getting shorts to ground, ect.....

My tail light lenses have also seen better days. it looks like there has been excessive heat, causing the housings to crack and melt here and there...so I am rebuilding them for now with epoxy and patches while I find some replacements. I bought all new bulbs today.

2 bulbs were worn at the bottom contact point and it looks like there could have been some arcing...but no real burn marks. I think they just wore out...Ill push the tabs up a bit in the housings receptacles to be sure good contact is being made.

Ill also add some dialectric grease to the contact points.

You can see where the gaitor makes a hard bend before it goes into the body. this is a rather poor design feature...but I guess they had to run the wiring somewhere!....its been a common issue on BMWs since the 80s. go figure!.

thanks for the help, diagrams and descriptions, guys.

hopefully it can help the community at large as Im sure it happens on the sedans too!

JP

[PichaDis11]

Nice! Glad you got it sorted.

[gbalthrop]

Originally Posted by 07lilredwagon

...You can see where the gaitor makes a hard bend before it goes into the body. this is a rather poor design feature...but I guess they had to run the wiring somewhere!....its been a common issue on BMWs since the 80s. go figure!...JP

Hi JP,

I also have a 2007 328xi E91, and even though mine has NOT YET had tailgate wiring harness issues (I have NOT looked under the gaiter), I have tried to evaluate how the design could be changed/improved.

It occurred to me that if the wiring harness were routed so that it went as parallel as possible to the hinge axis, the harness and wires inside would "Rotate" rather than "Bend," at least if the Gaiter were enlarged to allow rotation, and eliminate the "Bend."

QUESTIONS:
1)I have NOT taken the trim apart to examine how the harness is routed, but from what you saw in your repair, is that possible?

2) Is there room above the interior roof panel or "top liner" to extend the length of the harness enough to prevent bending, and make the wires rotate along their longitudinal axis RATHER than bending 90+ degrees every time the tailgate is opened?

3) Is there room either in the top of the Tailgate, or above the interior "top liner trim" to install connectors and make a custom harness extension or insert between the tailgate & roof/chassis?

Another reason to use the rear glass instead of opening the entire tailgate, especially in cold weather when the wire is less flexible.

Thanks,
George

[07lilredwagon]

Hey, George...

I should have taken some pics...but there are plenty out there...

let me try to answer your questions:

QUESTIONS:
1)I have NOT taken the trim apart to examine how the harness is routed, but from what you saw in your repair, is that possible?

There is a kit available, at least in Europe, to replace this section of wiring. I think, given the design of the car/wiring/loom/double tailgate-glass, ect this would be the only way to do it right.



2) Is there room above the interior roof panel or "top liner" to extend the length of the harness enough to prevent bending, and make the wires rotate along their longitudinal axis RATHER than bending 90+ degrees every time the tailgate is opened?

The wires do bend and rotate....its not the worst design...but after 12 years and heat and cold, and bending...THE CASINGS GET BRITTLE, CRACK AND THAT IS WHAT CAUSES THE WIRES TO BREAK....there are roughly 15 wires in there (a guess) going through that loom alone.


3) Is there room either in the top of the Tailgate, or above the interior "top liner trim" to install connectors and make a custom harness extension or insert between the tailgate & roof/chassis?

The designers worked very hard it seems to hide all this stuff and route things in specific channels and spaces inside the roof/housing/tailgate/hatch spoiler, ect, ect. Like VW, things like this are over engineered to a point hard to imagine!

Another reason to use the rear glass instead of opening the entire tailgate, especially in cold weather when the wire is less flexible.

so true....


I dont know what we can do to prevent this issue.....not much. it will become an issue...but for me, took 12 years or so...now its an older car....like those E36s and E40s from a few years ago!

Thanks,
George

[07lilredwagon]

btw, George...thanks very much for the detailed diagrams, ect. I had probed the connectors and sockets to be sure they were all working initially. I even tested the resistance in the bulbs. your diagrams helped confirm I was on the right track.

once I tested all the feeds, I began testing the ground side and viola, there it was, the misbehaving ground wire.

Incidentally, all, I ran a test of all the lights including the parking, brake, turn, reverse, 3rd brake light, hatch release, glass release, wiper, license plate lights, ect...and all seems good.

one little scare...car off, I mistakenly hit the turn signal lever and saw that I had a tail light and head light lit on that side. thought I had a bigger problem...but apparently our cars have this "feature" built in...weird!

turned the car to on...not running, cycled the blinkers and all was good.

JP