Lights Malfunction warning

[patomlin76]

Hi

Wondered whether anyone can give any pointers here.

For the past few weeks I've been putting up with a malfunction warning related to bulbs - the cold check it does at ignition.

The car passed the MOT test yesterday as there are actually no lights that are out. I'm led to believe that the voltage check the car does means that a failing bulb can trip the warning, not necessarily a blown bulb.

My S-Line has the Xenon headlights and LED rears, so I'm looking at all the halogen bulbs I can - front fogs, indicators, reverse lights and rear fogs.

Anywhere obvious I can start, or that is well-known for giving the bulb warning? The local specialist said I may as well start basic troubleshooting myself to save some money...

Failing this i know the cold check can be bypassed in VCDS (not my recommended course of action!)

Thanks. Paul.

[Crasher]

VCDS will have the appropriate code stored in central electrics.

[patomlin76]

Thanks Crasher...

On a 14 plate (which mine is) will VCDS point to a specific bulb or simply help narrow down the issue? I’ve noticed that A6s for example tell you in the display exactly which bulb is affected, mind just gives an unhelpful warning!

Having said that, I did prod around earlier at the bulbs I could access, and a reverse and rear fog bulb had slight blackening either side of the filament, so if the voltage reading is as picky as I’ve read, maybe they’re throwing the error reading up...

Thanks for your help anyway, next stop a proper code read!

Paul

[Crasher]

The A6 is a much more expensively engineered platform, you get what you pay for. The central electrics (AKA Onboard Supply Control Unit) of the MQB platform will detect which bulb(s) are causing it concern, a fault code reader does not do any diagnostic checks of anything, it just reads out the data stored by the cars onboard systems. The rear light unit bulb holders of the 8V are still having problems with an overloaded earth terminal which earlier models suffered from and multiple bulb codes point towards the appropriate earth.

[patomlin76]

Thanks

Would any code reader tell me the info I need (ie the plugin ones) or do you need the full vcds software? Just thinking about whether it would be worth getting one.

Cheers

[Crasher]

You would get a decent level of info with Carista without going to the level of VCDS.

[patomlin76]

Just to close the thread off, a local garage with vcds scanned and the diagnostics said faulty light switch. No idea why as everything works normally, must be a circuit board failing...

Anyway found a replacement switch unit, although a year or two newer, should be an easy swap in to clear the fault.

Thanks.


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[patomlin76]

Well, not quite the end of the thread just yet...

I found what looked like a decent light switch, but what I assumed was a revised part, not incompatible with my car. Original 8v0941531L, new 8v0941531AR

Fitted and turned ignition back on, sure enough a ‘bing’ and the same message appeared.

I then (wisely I think) invested in Carista as a decent budget scanner/code reader. It also threw up a light switch fault - VAG 930056 to be precise.

Am I now correct to assume the replacement light switch is NOT compatible? It did have a different icon for what was the front fogs - dipped and a cloud symbol - I thought that was purely cosmetic!

There were no further error codes from anything beyond the ‘central electronics’ switch, so hopefully I can rule out any physical headlight issue.

Thanks for helping (again!)



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[Crasher]

8V0 941 531 L has gone to 8V0 941 532 AE with the suffix 5PR as the colour code, I cannot track down the AR from home.

[dustinsteve3859]

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