Repairing Headlight Dimmer Switch

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pingu
Joined: Fri 30 Apr, 2004 17:01
Posts: 3337

  M roadster S50

Repairing Headlight Dimmer Switch

Post by pingu » Sat 27 Sep, 2014 17:07

I switched on the headlights and none of the the dashboard lights worked.

After checking the fuses, I suspected the dimmer switch (61 31 8 353 507).

Here are a couple of images of the switch...

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At first sight, it looks like it will be very difficult to repair without breaking it, but there is nothing I'll not do to try and save £50!!

Disassembling the switch is not too difficult if you have the thin bladed tools to lever the plastic apart without breaking it...

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Care must be taken removing the circuit board as it if firmly secured by plastic tabs.

The switching module MUST be in the position shown to remove it as the spring tabs (to lock it in the sidelight and headlight positions) are able to be released.

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Once the switching module has been released, the whole switch can be disassembled...

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and the dimmer module can be removed...

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and disassembled...

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(the image was taken AFTER the repair)

Although it was not the cause of the fault, the black part of the dimmer module had broken. The cause of it breaking was probably the driver forcing the switch too far clockwise or anti-clockwise. I repaired it with some superglue...

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The cause of the fault was a broken resistance wire...

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The maximum resistance I was able to measure was 19 Ohms, so I estimate the original resistance to be 20 Ohms.

I repaired the fault with some solder and filed it so it was flush with the spring and tested for continuity.

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After reassembly, I tested the switch for continuity between terminals 6 & 8. Fully dimmed (anti-clockwise)..

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and max brightness (fully clockwise)...

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The only difference between the original and the repaired switch is that minimum brilliance will be slightly brighter than before

- and I still have £50 to spend on fuel :)
Last edited by pingu on Wed 01 Oct, 2014 00:04, edited 1 time in total.
Pingu

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Brian H
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Joined: Tue 16 Dec, 2008 19:55
Posts: 2502

  Z3 roadster 3.0i

Re: Repairing Headlight Dimmer Switch

Post by Brian H » Sat 27 Sep, 2014 17:38

Nice write up, if the resistance coil is too far past it you can also put a jumper wire across the pins as shown below. This just puts your dash lights on at all times.

Image

Brian4
Joined: Mon 19 Dec, 2011 19:02
Posts: 534

  Z3 roadster 3.0i
Location: Hinckley

Re: Repairing Headlight Dimmer Switch

Post by Brian4 » Sat 27 Sep, 2014 18:49

Excellent write up. It must be the fun of taking things apart, finding the fault and then a solution that makes owning an older car fun.

The latest cars will be a pain to work on later in their life.

I have heard stories of one particular sports car that has a V8 that to change the back pair of spark plugs the engine has to come out, at least the plugs don't need changing for 80k miles.
Brian
3.0I Topaz Blue


2000 E36/7 Z3 3.0i
2016 F31 335d
2015 F21 118i

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pingu
Joined: Fri 30 Apr, 2004 17:01
Posts: 3337

  M roadster S50

Re: Repairing Headlight Dimmer Switch

Post by pingu » Sun 28 Sep, 2014 12:01

Brian4 wrote:Excellent write up. It must be the fun of taking things apart, finding the fault and then a solution that makes owning an older car fun.

The latest cars will be a pain to work on later in their life.
It becomes a problem when the electronic modules are gel-filled, but yes IT IS FUN :D .
Pingu

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lordhelpus
Joined: Sat 14 Sep, 2013 10:46
Posts: 128

  Z3 roadster 2.8
Location: Tax Exile

Re: Repairing Headlight Dimmer Switch

Post by lordhelpus » Sun 28 Sep, 2014 20:55

That's just the kind of thing that makes this site what it is...................well done pingu....top job. :bow
1997 2.8................ Montreal Blue

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Mint
Joined: Tue 01 Nov, 2011 18:43
Posts: 475

  Z3 roadster 2.2i
Location: Gayton (Staffordshire)

Re: Repairing Headlight Dimmer Switch

Post by Mint » Sun 28 Sep, 2014 22:51

Brilliant write up and photos Pingu. Well done, great ingenuity and a tank full of fuel into the bargain :)
Image
There are only two products required to make the universe work properly: Duct tape and WD40.
If it moves (and it shouldn’t): Duct tape. If it doesn’t move (and it should): WD40.

Cooper01
Joined: Tue 29 Apr, 2014 09:06
Posts: 152

  Z3 roadster 3.0i

Re: Repairing Headlight Dimmer Switch

Post by Cooper01 » Mon 29 Sep, 2014 14:09

Brilliant, make sure it goes into the knowledge base! Cooper

HighSharpe
Joined: Sun 28 Jul, 2013 00:01
Posts: 42

  Z3 roadster 2.0

Re: Repairing Headlight Dimmer Switch

Post by HighSharpe » Tue 30 Sep, 2014 22:17

Brilliant write up. To be honest, i hadn't realised that turning that knob made the dash lights dim :oops: Just tried it after reading this superb guide.

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