Kellydavies1976 Posted December 14, 2023 Share Posted December 14, 2023 (edited) Afternoon 馃枑馃徎 my 09 plate Audi a3 tdi has just failed its MOT. Apparently when my fog lights are in use my brake lights don鈥檛 work!! But they work independently of each other. Does anyone know how my husband might fix this. Many thanks 馃槉 Edited December 14, 2023 by Kellydavies1976 Quote Link to comment Share on other sites More sharing options...
Magnet Posted December 14, 2023 Share Posted December 14, 2023 Hello Kelly, Welcome and thanks for joining.聽 Simple things first - it could be a poor earth on one or both units.聽 If the earths prove to be OK:- possible fractured wire/s in the flexible harness section twixt tailgate and body, or the brake light switch maybe at fault.聽 Perhaps you could let us know how hubby gets on.聽 Kind regards, Gareth.聽 Quote Link to comment Share on other sites More sharing options...
cliffcoggin Posted December 14, 2023 Share Posted December 14, 2023 That's usually a sign of a bad earth at one of the light fittings. Remove all the bulbs and clean their contacts. Do the same for the contacts within the fittings. Ensure any earth leads from the fittings are unbroken and securely attached to the chassis. 1 Quote Link to comment Share on other sites More sharing options...
gerri Posted January 25 Share Posted January 25 (edited) Hi! You must pay attention: all four brake light bulbs work normally. If you turn on the fog lights, only two brake lights come on! If in this case only two brake light bulbs are working, they will be turned off when the fog lights are turned on! Edited January 25 by gerri Quote Link to comment Share on other sites More sharing options...
gerri Posted January 25 Share Posted January 25 7 minutes ago, gerri said: Hi! You must pay attention: all four brake light bulbs work normally. If you turn on the fog lights, only two brake lights come on! If in this case only two brake light bulbs are working, they will be turned off when the fog lights are turned on! 聽 Quote Link to comment Share on other sites More sharing options...
Stevey Y Posted January 25 Share Posted January 25 15 minutes ago, gerri said: 聽 Hi sorry we only got half of the posts Quote Link to comment Share on other sites More sharing options...
cliffcoggin Posted January 26 Share Posted January 26 Steve, I could see all of Piotr's message by scrolling left. Not that it matters because Kelly has not bothered to respond to the thread. 1 1 Quote Link to comment Share on other sites More sharing options...
gerri Posted January 26 Share Posted January 26 Sorry lads - it was my first post and I couldn't edit it. I hope next one will be better 馃槈 I am not sure at the moment I explained it correctly. The best way is to go to the car and check: If everything is OK and foglights are off FOUR brake lights bulbs are activated while braking. When fog lights are on ONLY TWO brake light bulbs are activated. And imagine the situation: two brake lights are broken (bulbs blown) and two are disconnected (because fog lights are on)聽 You have no brake lights on the back. Regards - Peter 1 1 Quote Link to comment Share on other sites More sharing options...
Stevey Y Posted January 26 Share Posted January 26 1 hour ago, gerri said: Sorry lads - it was my first post and I couldn't edit it. I hope next one will be better 馃槈 I am not sure at the moment I explained it correctly. The best way is to go to the car and check: If everything is OK and foglights are off FOUR brake lights bulbs are activated while braking. When fog lights are on ONLY TWO brake light bulbs are activated. And imagine the situation: two brake lights are broken (bulbs blown) and two are disconnected (because fog lights are on)聽 You have no brake lights on the back. Regards - Peter Hi thank you for that information, I did not know of that situation, just shows you you can learn something new every day,WELL DONE that man. Quote Link to comment Share on other sites More sharing options...
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