2015 A3 TDI - 2015 Audi A3 rear lamp short?

Honest John Back Room » Technical matters
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Sun 15 Dec 2024 12:12
2015 A3 TDI - 2015 Audi A3 rear lamp short? - carnut1980

Hi all, my OSR tail light (single filament) flashes with rear indicator/hazard lights. Its dull, but its definitely flashing with indicator!

Ive swapped bulbs over with NSR, and same thing happens!

When i did so, the NSR now has only tail light bulb flashing, as if it WAS the indicator!

I think its an earth problem, but all connections look fine, no corrosion within the terminals.

Could it be the black plastic Hella unit, that both bulbs are found within, which is held to the inner rear, by one screw, with a small black plastic holder, to turn it with? PNs PBT GF20, and 209212?

Genuine Audi part, but i can't seem to find it online, and there are no other visible part numbers?

Cheers guys!

Edited by carnut1980 on 15/12/2024 at 12:26

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Sun 15 Dec 2024 12:44
2015 A3 TDI - 2015 Audi A3 rear lamp short? - elekie&a/c doctor
Very likely to be an earth circuit problem . If the connector and pins show no sign of burning or overheating, then it could be an earth issue on the bulb circuit board. The metal contact strips on the bulb plate are just pressed into the plastic frame .
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Sun 15 Dec 2024 22:31
2015 A3 TDI - 2015 Audi A3 rear lamp short? - bathtub tom

Experienced exactly this problem, it was the (black) earth wire where it terminated on the body.

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Mon 16 Dec 2024 14:12
2015 A3 TDI - 2015 Audi A3 rear lamp short? - carnut1980

So the earth wire was shot? Not making contact? Cheers

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Mon 16 Dec 2024 14:32
2015 A3 TDI - 2015 Audi A3 rear lamp short? - bathtub tom

Corrosion at the connection.

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Mon 16 Dec 2024 14:48
2015 A3 TDI - 2015 Audi A3 rear lamp short? - elekie&a/c doctor
More likely burnt/ overheated. See this on a daily basis.
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Sun 29 Dec 2024 14:36
2015 A3 TDI - 2015 Audi A3 rear lamp short? - carnut1980

Is there any way i can upload photos here?

Basically i swapped over with the NS unit, and problem persists, so if tis an Earth issue, its further up the car? From wiring loom, forwards

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Sun 29 Dec 2024 15:11
2015 A3 TDI - 2015 Audi A3 rear lamp short? - elekie&a/c doctor
Carefully inspect the multi connector that plugs into the lamp unit . The earth circuit is the brown wire . You could add a wire into this location and ground it as a temporary test .
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Sat 1 Feb 2025 16:14
2015 A3 TDI - 2015 Audi A3 rear lamp short? - carnut1980

Cheers.

Failing that, is it possible that the rear demister also not working, is related to this problem?

Do both wires use the same loom?

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Sat 1 Feb 2025 16:54
2015 A3 TDI - 2015 Audi A3 rear lamp short? - elekie&a/c doctor
Is this a cabriolet model?
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Sat 8 Feb 2025 22:24
2015 A3 TDI - 2015 Audi A3 rear lamp short? - carnut1980

No, 3 dr 2.0 TDI 184 hatch, 64 plate

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Sun 9 Feb 2025 00:01
2015 A3 TDI - 2015 Audi A3 rear lamp short? - elekie&a/c doctor
Have you sorted the rear light fault ? Is the hrw issue another problem or did it occur at the same time?
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Sun 9 Feb 2025 17:01
2015 A3 TDI - 2015 Audi A3 rear lamp short? - carnut1980

Hrw occured first, i think. Indicator flagged up as advisory on MOT a month ago, but of course, could have been going on for longer! The terminals/connectors direct to the bulb, look fine!

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Sat 1 Mar 2025 13:22
2015 A3 TDI - 2015 Audi A3 rear lamp short? - carnut1980

re. this issue, the NS (good) side has 3 earth wires attached, to the body, behind the rear trim that covers the back of the indicator assembly, but the OS has only 2!

I took pics, but can't seem to add them!

I had a feel around, but there doesnt seem to be a 3rd earth lead thats broken loose.

The 2 earth wires that ARE present, are perfectly sound.

Is it even worth bothering with, as its only an advisory, and i will be selling the car soon anyway? cheers

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Sat 1 Mar 2025 13:39
2015 A3 TDI - 2015 Audi A3 rear lamp short? - elekie&a/c doctor
If it’s only an advisory, there can’t be much wrong with it. If it’s a multi bulb light , then only 50% of it needs to work for a mot pass .
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