# Rear Light Cluster zapped



## Stanmer (Jan 15, 2017)

Hi,

My drivers side rear light cluster has failed (all sensors started beeping at once, and no visible bulbs gone, so I don't think it's bulbs). I've taken it apart and one of the six connector prongs that the plus attaches to looks a bit zapped - as per the photos. The prong is discoloured, bent and corroded and more worryingly the plastic around it seems to have gone somehow. Tracing the metal tracks around the bulb housing, it seems to be the one that goes to all of the bulbs.

The plug that connects to the bulb housing is also looking a bit ropey around the corresponding slot to that prong.

It's been quite wet. However, no water came out of the light cluster. I know they can fill up and was expecting that to be the problem, but can see no trace of water causing the problem.

Does anyone have any ideas what has caused it and how I fix it? Will I need a new bulb housing and plug - if so, any ideas what the part numbers are?

Many thanks for any advice!


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## -:[KM]:- (May 16, 2010)

Cause - poor return connection
Remedy - new bulb housing and new plug

Your details do not show where you're from. Idiots like me have so many spares.


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## Stanmer (Jan 15, 2017)

Thanks KM - I suspected as much. I've been having a fiddle but it looks shot. I'm in Brighton, UK if anyone local has any spares they would care to sell. Otherwise I will get myself online and look for the parts.


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## DowneasTTer (Aug 9, 2017)

Stanmer said:


> Thanks KM - I suspected as much. I've been having a fiddle but it looks shot. I'm in Brighton, UK if anyone local has any spares they would care to sell. Otherwise I will get myself online and look for the parts.


I think the price for a replacement from Audi isn't that bad. Here in the states it's only $60.00 or so. That's after a nice trip over the pond. That said if you keep the car long enough it will happen again and again. What I did was bypass the ground wire in the plug. I drilled a small hole in the plastic next to the ground strip inside the light. Put a SS bolt and washer through the light and then ran a I think 16 gauge wire to a bolt on the frame creating another ground pathway. I did put a quick connect on the ground wire to make light replacement easier.


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## brittan (May 18, 2007)

There are many threads about this problem. The earth pin is simply not large enough to carry the current of all the bulbs.

See this: viewtopic.php?f=43&t=332559 (sorry, picture removed by photobucket)

Also this: viewtopic.php?f=19&t=1299345&p=7103561&hilit=rear+light#p7103561
which does still have my pictures. Having noted the issue and a solution I added the extra earth wire before the problem arose.

For info the part numbers for the bulb holders are:

8J0945257 bulb holder left
8J0945258 bulb holder right
1J0973733 Housing (the connector plug)
000979225EA Wires (repair wires yellow)


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## robbiepepper (Apr 4, 2017)

It looks repairable to me if you follow the thread on better earthing shown by Brittan [smiley=book2.gif]


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## Barr_end (Oct 19, 2016)

brittan said:


> There are many threads about this problem. The earth pin is simply not large enough to carry the current of all the bulbs.
> 
> See this: viewtopic.php?f=43&t=332559 (sorry, picture removed by photobucket)
> 
> ...


This...
But don't bother leaving it to a new oem set up, as the problem will only return. As Brittan said, the connection is simply not big enough. Do the extra earth mod and forget about it


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## Stanmer (Jan 15, 2017)

Cheers all. I put it back together a final time expecting to order new kit and it had done an MFI (Magically Fixed Itself). However, I suspect that's just luck, with the fried earth prong just about making contact, and it will go again soon. At least it meant I didn't rush out and but the new parts and can now do the earthing mod at a time that suits me (i.e. not in the dark after work!)


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## SwissJetPilot (Apr 27, 2014)

I decided not to use an external ground point used in the Youtube video, and instead used the two OEM ground lugs that are inside the trunk (Roadster shown) to avoid future corrosion issues. Both ground lugs are in close proximity to the rear lights and work perfectly for this application. The one shown is on the left side near the base of the amp, and there's one on the right side is just aft of the battery.

Getting the ground wire through the grommet is a bit tricky. Just blunt-cut the wire and work it through. Then once you have it where you want it, strip the ends and attach the terminal connectors. Choice of terminal connectors is up to you, bullet or spade works fine. For the SST bolt, I went with a pan-head as it provides a wider contact surface with the ground trace. If the bolt is a bit too long, cut it as close to the nut as possible.

1.) Disassemble the light assembly and drill a hole through the grey plastic housing, close to the ground trace. 
2.) Insert a SST pan-head bolt through the hole, ensure a good contact with the screw head to the ground trace. 
3.) Cut a piece of 2.0 - 2.5mm diameter ground wire (Audi cars use brown, but any color works) aprox. 6 - 8" long. 
4.) Connect a ring terminal to one end of the ground wire and a male bullet (or spade) connector to the other. 
5.) Place the ring terminal onto the screw (between the two washers) and secure with a Nylock nut.

Re-assemble the tail light assembly, it's now finished. Repeat for the other side.

6.) Cut a 1-meter piece of ground wire and route it through the tail light grommet (easier from outside to inside). 
7.) Route to the closest existing chassis ground-lug and cut to proper length.
8.) Attach a ring connector to the one end and a female bullet (or spade) to the other end. 
9.) Connect the ring connector to the chassis ground lug.
10.) Connect the two bullet connectors and re-install the tail light assembly.

Repeat for the other side and you're done.

Hardware: 
3 meters of 2.0 - 2.5mm diameter ground wire
Ring connector (x4)
Male bullet or spade connectors (x2) 
Female bullet or spade connectors (x2)
SST pan-head bolt (x2), washers (x4) and nyloc nut (x2)


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## Stanmer (Jan 15, 2017)

That's a really useful guide, thanks.


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## SwissJetPilot (Apr 27, 2014)

No worries, it's pretty straight forward. I pulled both lights and did them one evening in the comfort of my workshop (aka - kitchen table). Then the next morning I went out, pulled the trunk panels, routed the chassis ground wires, installed the rear lights and that was it. 

One other comment - this is a good time to replace all the lamps while you have it all apart. Mine were coming up on 10-years old, and I could see the silver diffusion inside the glass on a couple of them. So I replaced them at one go, both sides. Just one less thing to worry about for another 10-years.


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## mickee92 (Mar 2, 2016)

SwissJetPilot said:


> No worries, it's pretty straight forward. I pulled both lights and did them one evening in the comfort of my workshop (aka - kitchen table). Then the next morning I went out, pulled the trunk panels, routed the chassis ground wires, installed the rear lights and that was it.
> 
> One other comment - this is a good time to replace all the lamps while you have it all apart. Mine were coming up on 10-years old, and I could see the silver diffusion inside the glass on a couple of them. So I replaced them at one go, both sides. Just one less thing to worry about for another 10-years.


That earth wire looks pretty thick does it matter that I used just typical earth wire pulled out of domestic white flex??

It solved the problem I suppose but in terms of the right resistance etc or what ever is determined by wire gauge I should be ok by using it?


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## SwissJetPilot (Apr 27, 2014)

I can't speak to the wire you used, but the 2.0 - 2.5mm diameter seems to work fine for this application. The green-yellow is actually the standard French automotive ground, I bought mine from a local Renault repair shop. The Germans (Audi) typically use brown for ground.

Consider the size of the metal traces in the housing and you'll realize the 2.0 - 2.5mm is really not an issue in the grand scheme of the circuitry in this particular application. The whole purpose of this exercise is to reduce the high current state at the ground connector pin, which is why its burnt in the first place.

For our North American friends, 2.0 - 2.5mm is roughly equal to 12 AWG.


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## Stiff (Jun 15, 2015)

Fantastic and useful guidance as ever Swissjet.


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## mjh2222 (Feb 2, 2019)

Thank you for this guide.

Is it ok to do this application without replacing the bulb holder and burnt connector?

Thanks,


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## tttony (Dec 21, 2014)

Yes, provided it is only the earth connection that is burnt.


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## mjh2222 (Feb 2, 2019)

I have just bought the wire for my burnt pin, I have the same issue.

Can I just check that the 0.5mm is the correct size?

Audi said they have either 0.5mm or 1mm so we went with the 0.5mm.

Thanks


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## SwissJetPilot (Apr 27, 2014)

You want to add a larger wire, not the same size as what's in the connector. The recommended additional earth/ground wire diameter is 2.0 - 2.5mm or if you're in North America, use 12 AWG.


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## mjh2222 (Feb 2, 2019)

Oh that is a good point, because then it would last longer before frying again.

Bugger I have got the 0.5mm now lol. Audi only had that and the 1mm, I am guessing I would need to buy it from somewhere else to get 2mm or 2.5mm.

I will use the 0.5mm this time as I have it already and then next time I will get the bigger one, thanks for the tip.

*Edit, I am in the UK, Sheffield.


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## tttony (Dec 21, 2014)

The size of the original earth wire is not the problem, it never heats up and burns. The problem is with the earth pins/sockets in the multiplug being undersized for the current they have to handle when all the bulbs (or most of them) in the light unit are powered at the same time.

A brown cable rated at 8amps is more than adequate for the earth modification. In the UK, Halfords sell such cable on little reels.


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## mjh2222 (Feb 2, 2019)

Thanks for that. Do you mean use the 8 amp wire from Halfords in place of the 0.5mm wire I got from Audi? Or are you talking about doing the mod where you drill a hole in the bulb holder etc?

The 0.5 wire I got today has clips at the ends.


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## tttony (Dec 21, 2014)

I guess that Audi sold you one the range of yellow "repair wires" which are available with all the various pins/sockets that Audi/VW use. If that's the case, just ignore it and buy the brown cable from Halfords and use that for the earth modification.


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## mjh2222 (Feb 2, 2019)

Thank you

Could you link me to the correct wire? Do I have to say how long to make it?

I could take this yellow Audi wire back and get the halfords one if it is going to stop it happening again.

I can just tell the garage to use the halfords wire instead to fix it.


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## tttony (Dec 21, 2014)

O.K. I wrongly assumed that you were going to be doing this yourself.

Any decent garage should have some suitable brown cable to hand, but I suggest that you will be better off using a specific car electrician rather than a general repair garage. Just tell them that the wire needs to be 8Amp or greater.


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## mjh2222 (Feb 2, 2019)

Ok I will do exactly that. Thank you for your help and advice on that.


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