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      11-18-2017, 03:50 PM   #1
UK_Nomad
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DIY : 2007 E93 LED tail light repair

The LED strips in the rear lights have been out for a while, now the car is back on the road it's time to get them working as they should.

Background info :

I bought a spare pair of lights as one of my orignals was cracked, this made me a lot more relaxed about cutting the lights open.

Most of the lights on the car use normal bulbs (1 each), there are also 4 sets of LED strip lights (both back lights, and 2 in the bootlid).

The LEDs are part of a sealed light unit, if they fail, BMW expect you to buy a new light assembly

I have seen a light with 1 bar out and 2 bars working, mine had 1 faulty LED that stopped all 3 bars - fix the 1 faulty LED and all 3 work again.

The LEDs out didn't show any warnings on the dash so be aware you might have lights out and not know.

Tools required :
8mm deep socket to remove the light cluster from the car
Torx to remove the bulb holder from the light unit (thanks BMW - why make life easy)
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      11-18-2017, 04:08 PM   #2
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Time to dismantle the sealed light unit

1. Before starting, look carefully to see how the outer lens lines up with the light assembly !

2. Remove the black "eyebrow" piece (look for 3 simple "barb" fittings)

3. Cut around the outside of the light - the red outer lens will then just drop off.

4. Unhook the 4 "barbs" at the back of the unit and push the middle moulding off the backing piece. It will need a bit of levering as it's a tight fit.

5. Note how the wires are routed then unclip the circuit board and remove it from the light.


Tip :
I cut around the red outer lens so I could remove it gently, expect it to crack if you try remove it using too much force.
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      11-18-2017, 04:38 PM   #3
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Diagnostics time

I was expecting to find some dry solder joins ( I've see other folk say this was the problem with their lights, and we all know LEDs last forever ... right ?)

You can use a 9 volt PP3 battery to test the circuit on the bench (connect the blue wire to battery postive)

Connect the battery then either :
Option A - look around each LED, if you see any dry solder joints - resolder them and hope it's fixed (all of my problems were due to dead LEDs not dry joints).
Option B - use a multimeter to measure each LED, check the voltage across the pins of the 1st LED, then across the pins of the 2nd LED etc ... working LEDs give voltages under 3 volt, faulty LEDs show over 6 volts.
Option C - use a small screwdriver, short the pins of each LED in turn until the unit lights up.

Note. LEDs must be connected the right way around, if you connect them "backwards" nothing will work (think of them as a 1-way valve for electricity)

You should then know which LED is faulty.

You can hold a new LED in place across the faulty LED to check things work, then make a note so you fit the new LED the right way around.

replace the faulty LED first - retest and you should now have 3 working LEDs


Optional - replace the other LEDs so you have a matched set.
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      11-18-2017, 05:01 PM   #4
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LEDs come in all shapes & sizes ... pick one you like and hope for the best

Industry standard LEDs are 5mm but 3mm is also fairly common.
BMW have decided to do their own thing and use a size that nobdy has ever heard of (short, tapered, red, 4.2mm, superbright, a focussed light pattern) - which makes it impossible to get replacements.
This shouldn't be a problem but as the BMWs ones are failing within a few years (most other LEDs are expected to last forever), we have a problem

Process of elimination means I ordered replacements :
5mm
Red
Superbright
*NOT* diffused

I thought the BMW LEDs sent a tight beam of light so I got some that were viewable for about 40 degrees, if I was choosing again I'd pick something more like 90-120 degree range .

The original LEDs used a plastic mounting block, the new ones are fitted without the block.

Note where the orignal LEDs were mounted - the new ones have to be in the same place to work properly with the light bars :
a couple of mm above the board.
a few mm inset from the edge of the board (this is critical for the reassembly)
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      11-18-2017, 05:25 PM   #5
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Assembly is fairly simple but there are a couple of "Gotchas" :

clean / hoover everything before starting !
- the last thing you want is a fingerprint or chunk of loose plastic on view inside the lens when you're finished.

clip the repaired circuit board in place
- route the wires as they were

refit the middle moulding
- make sure the 4 fixing barbs click into place correctly.
- each lightbar has a recess at the end - the LED should sit in the recess. closely inspect each LED to make sure it's not been pushed out of place.
- use the PP3 battery to retest and make sure everything is working properly.

refit the black eyebrow piece so you have a good reference point for the next stage.

glue the red outer lense in place
- I used several spring clamps to hold the lens while the glue set.

refit to the car when the glue is dry (feeling rather smug is permitted at this point)


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      11-18-2017, 05:37 PM   #6
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Comments / feedback welcome, let me know if this type of guide is worth doing, what works best - what doesn't work so well ???

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      03-16-2018, 10:56 AM   #7
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Very useful thread! Thanks for this DIY, going to try this myself asap!
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      03-18-2018, 07:38 AM   #8
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Thanks, UK_Nomad.
Awesome manual!
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      03-18-2018, 07:56 AM   #9
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Thanks UK_Nomad for this DIY, going to try this on my E39 taillight
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      03-19-2018, 05:33 PM   #10
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Glad to know people are finding this guide helpful.
If you work out a better way of doing things when you try the repair please add a note here to help others in the future.
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