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      09-14-2018, 03:38 PM   #1
HarryFD
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Getting My Trunk Light to Work

I noticed my trunk light was not working. I checked the bulb and the fuse and they are ok. I checked for voltage at the bulb base with none found.

I read that the switch for the light in in the rear trunk latch. I removed the trunk latch and found a two wire connector (with brown wires) laying loose in the area. It appears to the be the same wire on the lamp holder.

I am unable to find where this connector plugs into. There was no area on the latch mechanism for this wire to plug into.

Does anyone have a picture showing where the connector is located or can tell me where to look?
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      09-14-2018, 04:03 PM   #2
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Looks like there is a connector right on the latch unit.

https://www.ecstuning.com/b-genuine-...k/51247840617/
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      09-14-2018, 05:32 PM   #3
HarryFD
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Quote:
Originally Posted by gpraceman View Post
Looks like there is a connector right on the latch unit.

https://www.ecstuning.com/b-genuine-...k/51247840617/
Thanks! Unfortunately that is the one I have. There is a connector on the left side there but it is in use. My two wire connector is on the right side is there are no corresponding connectors anywhere near this connector.
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      09-14-2018, 05:57 PM   #4
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I looked again at the latch, two wire connector and itís position relative to the latch. The connector does not reach the latch! The green connector goes tot he third rear brake light.

Here is a picture of the connector and it's position relative to the latch.
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Last edited by HarryFD; 09-14-2018 at 06:19 PM.
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      09-15-2018, 01:04 PM   #5
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There is an extra connector in the area of the third brake light that doesn't go anywhere.

Is the light switch in the trunk lid, or in the other side of the latch in the body?
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Last edited by StickMon; 09-15-2018 at 11:52 PM.
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      09-15-2018, 05:00 PM   #6
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Quote:
Originally Posted by StickMon View Post
There is an extra connector in the area of the third brake light that doesn't go anywhere.

Is the light switch in the trunk lid, or in the other side of the latch in the body?
Thanks! This means the power for the light comes from the multipin connector plugged into the trunk latch. I presume this means that if all is ok, I should see 12v at the striped wire at the lamp. I will check when I can.
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      09-15-2018, 11:59 PM   #7
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I'm assuming that the module linked above contains the servo that opens the trunk when the button in the cabin is pressed.
Are we sure that's the same thing that turns on the light, or is there just a simple micro-switch somewhere else?
The WDS is down again, or I would consult the schematics.
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      09-16-2018, 03:01 PM   #8
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Quote:
Originally Posted by StickMon View Post
I'm assuming that the module linked above contains the servo that opens the trunk when the button in the cabin is pressed.
Are we sure that's the same thing that turns on the light, or is there just a simple micro-switch somewhere else?
The WDS is down again, or I would consult the schematics.
Thanks for offering to look.

Assuming this is the standard DIN wire codes. Brown would be a direct connection to ground and brown with a stripe is a switched ground.


I do not have the wiring schematics.

I have been looking to see if the wiring schematics are available on the web. Can you send me the link?
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      09-16-2018, 08:35 PM   #9
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It's intermittently:
http://www.bmw-planet.net/diagrams/r.../e85/index.htm
but they seem to have lost their DNS registration again.

Just had a peep inside my trunk and I guess the light switch must be inside that module.
There's jack squat anywhere else.
If they pull that off with only 3 pins, one must be +12V, one must be power to the light (with the other side of the light grounded), and one must be switched to ground to energize the unlock servo.
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Last edited by StickMon; 09-16-2018 at 08:42 PM.
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      09-16-2018, 10:16 PM   #10
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Quote:
Originally Posted by StickMon View Post
It's intermittently:
http://www.bmw-planet.net/diagrams/r.../e85/index.htm
but they seem to have lost their DNS registration again.

Just had a peep inside my trunk and I guess the light switch must be inside that module.
There's jack squat anywhere else.
If they pull that off with only 3 pins, one must be +12V, one must be power to the light (with the other side of the light grounded), and one must be switched to ground to energize the unlock servo.
Stickmon:

Thanks for the link. I have this stuff for my 911 and Bus but not the Z4. It is incredibly handy for stuff like this.

This afternoon I had some time to do some testing with my voltmeter. With the trunk lid open, I have 12 volts on one side of light. The ground side is open. When I connect the ground side of the light to the negative terminal of the battery, the light illuminates. This is tells me that my ground is missing.

A fellow posted a wiring diagram on the Bimmerfest BBS.

It looks like the trunk switch switches the ground for the light.

I did some more testing. Terminal 3 goes to ground as required. It appears the wire from terminal 1 of the latch connector to the light does not have continuity. I am thinking the area that flexes between the body and trunk lid has a broken wire. When I have some time, I will look into this.
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Last edited by HarryFD; 09-17-2018 at 12:20 AM. Reason: Typo. Meant Terminal 3 not 1.
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      09-16-2018, 11:51 PM   #11
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Yep. Pin 3 should definitely be ground.
Odd though. If pin 3 isn't grounded, the remote unlock shouldn't work.
I'm guessing that the left unmarked terminal of M17a is pin 2 and is the drive for the unlock servo.
These would be on another schematic for central locking.
The middle unmarked terminal of M17a may not go anywhere.
Either that, or the connector actually has 4 pins, and that's the "hey you're driving with the trunk open" indicator.
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      09-17-2018, 11:17 PM   #12
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After testing, I verified the wire between the trunk release and the light was broken. I removed the flex connector between the trunk lid and the body. I found the brown with yellow stripe wire which provides the ground for the light was broken. Soldered in a splice and all is working again.

Thanks to all who helped!
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      09-18-2018, 12:17 AM   #13
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Where exactly was the wire broken?
This sounds like one of those "this will happen" things that several of us will eventually encounter.
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      09-18-2018, 12:20 AM   #14
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Quote:
Originally Posted by StickMon View Post
Where exactly was the wire broken?
This sounds like one of those "this will happen" things that several of us will eventually encounter.
It as an inch or two inside the flexible tube at the end closest to the trunk lid. Several other wires look to be on the verge of failing and I will address as needed when the time comes.
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