audi a3 rear lights

[wilkesneil]

just purchased and fitted led rear lights on my a3 2004. all light are working fine but when i start car or put ignition on it says left brake light out. upon inspection all lights are correctly working as they should. is there a way to reset the electrical sensors or shall i just leave it as it is and take it that the car knows its supermarket part...

[Hymie]

Vehicles with lamp failure detection determine this from the current flow when the bulb is illuminated. It is likely that you have wired the extra lights within the left brake light current sensing circuit – resulting in the warning (due to excessive current flow).

Normally this current sense circuit is in the return path – therefore if you find an alternate chassis location to ground the extra lights, this may fix the problem.

[ChuckFickens]

I'm going to go the other way to hymie.

I reckon the lower current that LED bulbs draw is likely to be triggering the warning by dropping it below the threshold it will see as open circuit (as if the bulbs had blown)

[Hymie]

ChuckFickens may well be correct if you have replaced the standard lights with LED types – but from your post, I was under the impression that you were adding additional lights to the car.

[wilkesneil]

chuck. this is what i was thinking but was wondering if there was a way to turn off or reset the sensor. i know led's have low current but weren't to sure if through drop in current would cause the sensor ti be activate.

[AlBags]

There isn't mate.
The kit ought to have a device with it to wire in and stop this happening.
Try an email to the kit supplier or manufacturer ... and check any/all of the rear lamp earths.

[Hymie]

If I owned an A3 it would annoy me to have an erroneous warning because I had fitted LED brake lights.

There is a way of increasing the current such that the vehicle does not detect the low current as a fault - and that is to add a resistor in parallel with the LED bulb.

A normal 21W brake bulb will draw around 1.5A. Given that the right brake light current is sufficient not to cause the problem, you probably only need an extra 0.3A or so in the left brake circuit to fix the problem.

Maplin sell a 47R resistor rated at 7 watts for 59p.

http://www.maplin.co....rewound-resistor-2179

14V across this resistor will draw 0.3A and dissipate 4W (feeling warm to the touch).

You will need to workout which wires are connected to the brake light and attached the resistor in parallel.

[AlBags]

I had to resort to trickery on the GTR rear lamps to rig up a pair of fogs (on the inner pair of lamps) with diodes to save fitting a naff separate fog. (Jap import .. no built-in fog) That will probably work mate.

[wilkesneil]

hymie, that is great that a small thing at small cost and Will look into it.

al, as my electrical knowledge isnt all that good i think i Will just bear with it and maybe get someone to sort it out once the yellow light on dash does my head in.