B6 A4 license plate light not working

[laughoutlao]

Hey guys , i have a 2002 Audi A4 Quattro and I'm currently having problems trying to figure out why my license plate lights aren't working. I tried to remove the trunk panel to see if there's a loose connection but didn't see any. Is there a fuse somewhere that could cause this issue or some module or sensor that can fix this issue


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[imnuts]

Is it only one? Does it have a bad bulb or are the contacts in it corroded?

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[DenverAudiInnie]

^^ +1

Replace the bulbs for a few bucks and remove the housing completely to clean the contacts with sand cloth. Should fix you right up.

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[ShadowSmitley]

Just had this happen to me last night. My left light housing had the left terminal corroded apparently and the plastic that holds the metal pin broke. I bought a new set of fixt uses from ECS for around $44.

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[laughoutlao]

Thanks for the input guys , this is the left side and what it looks like right now . Could this be the issue




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[ShadowSmitley]

That's definitely your issue. The left pin is corroded so it is not letting the bulb holder contact the metal to send the current to the bulb. The whole black piece comes off and you should be able to clean it. pretty easily. Just be careful as things tend to break easier when they are already corroded.

[Spike00513]

That's definitely your issue. The left pin is corroded so it is not letting the bulb holder contact the metal to send the current to the bulb. The whole black piece comes off and you should be able to clean it. pretty easily. Just be careful as things tend to break easier when they are already corroded.

Not sure what that's called. Oxidation? Corrosion?

I never really learned how to care for electronics yet.
Not just the subject of how to remove any corrosion (such as what tools, chemicals, etc. are required)
but also the final step of protecting it after.

Because for example, if you are mechanically abrading the surface, maybe you strip it down to bare fresh metal. Which is then exposed to the outside environment.

I hear one product is called Stabilant 22A. It's probably expensive. I heard it might be favored over dielectric grease, for use in connector housings, because they have metal pins inside.
IDK if this gets applied at the factory.



Oh look, Audi and VW logo branding.



But at this point if OP is already taking apart, maybe it doesn't matter and isn't that big of a deal.

I mean, let's say he puts it back together and it works for another 5 years until having to do it again.
Would a chemical make it last 6 years?
Who cares.

Maybe this is more of a concern for a factory assembly line, to extend the life of the car as much as they can, so it doesn't corrode early in vehicle ownership, and everybody starts complaining about how their low-mi fancy Audi is having issues.

Ordering something like that, you're waiting for it to ship.
Versus fixing something by hand right now.
Maybe you'll need to get creative with a fix. A cut piece of emory cloth or sandpaper wrapped around a Q-tip?
Not sure.

Maybe whoever buys the car next down the road, will have to do it again.

[laughoutlao]

That's definitely your issue. The left pin is corroded so it is not letting the bulb holder contact the metal to send the current to the bulb. The whole black piece comes off and you should be able to clean it. pretty easily. Just be careful as things tend to break easier when they are already corroded.

Sweet I appreciate the response man I'll attempt to sand it down and see if it works


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[imnuts]

A Dremel with the wire brush tool works well to clean off corrosion on those parts.

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[Chemmie]

Brass contacts, brass being a mixture of Cu and Zn, for the most part. Cu oxidizes with other constituents in the atmosphere to form the green cupric carbonate you see on the left contact. Copper does react with pure oxygen to form cupric oxide in a classic RedOx reaction but that's not quite the case here, but if left alone eventually it'll turn to cupric oxide. I'll leave it to the inquiring mind to research redox rx'ns and determine *why* the galvanic corrosion is on only 1 contact. Note for this electrons travel in the reverse direction of current.

Mechanically clean it, or a strong acid will dissolve the oxide layer. Theory behind this is exactly why we use acidic flux prior to soldering wire or copper pipes.

The Canadian cars have DRL's, which in conjunction with the generous piles of salt they spread on the roads ensures our license plate and fog light sockets get corroded out of their sockets.

[laughoutlao]

Alright I'm at loss here , just found this while trying to figure out why my license plate lights don't work. Looks like someone rigged up something here ? What is this ?


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[ShadowSmitley]

That looks like they tried to wire something else into the license plate lights to turn on with them, maybe like a light up 4 rings badge. Are you able to see the other end that it needs to connect back to? Whatever it was, they did a really shitty job and wiring it. Did you get one side to work at least?