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Thread: Brake Lights Flickering Poss ABS Fault?

  1. #1
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    Brake Lights Flickering Poss ABS Fault?

    OK so I've sorted the injector issue out and now another fault has cropped up! What I thought was a blown bulb/wiring I'm now thinking this issue is somehow connected to the ABS unit.

    Issue: All three brakes lights will illuminate/flicker when I am not operating the brake pedal. If it doesn't do it when I fire up the iginition then if I put the side or headlights on I get the 'blown bulb' sign in DIS as the rear brake lights come on/flicker. If I pump the brake pedal when the engine is running to build pressure the blown bulb light goes out and the brake lights operate as normal. I've also noticed on occasion what sounds like a relay sticking (clicking on/off) which appears to come from the ABS unit (big one the metal pipes connect into) under the bonnet. I'm thinking the two are related.

    I'm not aware of there being any faults recorded given that I've just had it checked for the previous fault and it might be intermittant. I've tried disconnecting the battery to re-boot but it still comes back.

    Is there a relay in the ABS unit? Any other things I could check before focusing on the ABS unit itself as that won't be cheap!
    At the Annexe: 2004 TDI SE (90Bhp) Mauritius Blue, 16" 5 Spoke alloys, Satellite cloth, Parrot Bluetooth
    On the Drive: 2004 TDI SE Mauritius Blue, Black cloth, Concert II, CC, Parrot CK3000 Bluetooth (Fitted by Skipton) & 2003 TDI SE, Cobalt Blue, Black Leather, Sydmeko armrest, PDC, DIS, Alu Pack, S3 Leather Gear Shift, CC, Concert II, Parrot, Performance Discs, Stealth re-map. Bought from here courtesy of Havank.
    In the Garage: 1993 Porsche 964 Celebration. Polar Silver, Big Hips

  2. #2
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    It's more probable to be the brake light switch on the pedal or master cylinder (unsure which on the A2)

    The ABS (As far as i'm aware) cannot illuminate the brake lights on the A2. The blown bulb sign in DIS could also point toward poor contacts or an earth problem somewhere between the light clusters and the main wiring. Somebody with a little more knowledge of A2 wiring will be along shortly i'm sure, but there is bound to be a common earth point somewhere along the way.

    Nick
    2003 Audi A2 1.6 FSI Sport | Bi-Xenon Projectors | Climate Control | Front Fogs | Headlight Washer Jets | Heated Mirrors & Windscreen Washer Jets | Heated Seats | Symphony II | Vanity Mirrors | PDC | Rear Electric Windows | Auto Dimming Rear View Mirror | DIS | Working OSS | Rear Cup Holder


  3. #3
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    I'm thinking it's the brake switch i did mine a few weeks ago my light's where intermittent sometimes came on sometimes didn't it sounds like yours are inbetween the parts 10 from gsf or about the same from euro car parts and about 20 mins to fit.

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  4. #4
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    Quote Originally Posted by justjust73 View Post
    I'm thinking it's the brake switch i did mine a few weeks ago my light's where intermittent sometimes came on sometimes didn't it sounds like yours are inbetween the parts 10 from gsf or about the same from euro car parts and about 20 mins to fit.

    Sent from my SM-J510FN using Tapatalk
    Is that the brake switch that activates on the pedal? If so how easy is it to access/replace before I put myslef in danger of pulling my back? I too was thinking porr earth/switch......
    At the Annexe: 2004 TDI SE (90Bhp) Mauritius Blue, 16" 5 Spoke alloys, Satellite cloth, Parrot Bluetooth
    On the Drive: 2004 TDI SE Mauritius Blue, Black cloth, Concert II, CC, Parrot CK3000 Bluetooth (Fitted by Skipton) & 2003 TDI SE, Cobalt Blue, Black Leather, Sydmeko armrest, PDC, DIS, Alu Pack, S3 Leather Gear Shift, CC, Concert II, Parrot, Performance Discs, Stealth re-map. Bought from here courtesy of Havank.
    In the Garage: 1993 Porsche 964 Celebration. Polar Silver, Big Hips

  5. #5
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    Yes thats the one you just remove the lower cover near the pedals there's 2 one for the clutch one for the brakes the brake one has 4 pins the clutch has 2 they push and twist in.

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  6. #6
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    Update. Right I've bought the plunger type switch (pattern part it would appear) and fitted it. Harest job was taking off the lower dash trim to actually get to it. But the problem is still there.

    When left on ignition the brake lights will occasionally flicker. Pumping the pedal stops it usually accompanied by the 'blown buld' sign in DIS which clears. It could be that the part if defective so I've had a play with the originial one and plunges OK along with lights on/off as required so refitted it. Now I get the problem eveytime I apply the brakes I get the alarm for blown bulb in DIS, which clears after a few seconds only to come on again when I apply the brakes! All the bulbs are fine.

    I'm now going to take off the switch from our 2004 car as I know that's OK and try it on mine this weekend. If all good it's definitely the switch, if not then I've got a wiring fault somewhere.
    At the Annexe: 2004 TDI SE (90Bhp) Mauritius Blue, 16" 5 Spoke alloys, Satellite cloth, Parrot Bluetooth
    On the Drive: 2004 TDI SE Mauritius Blue, Black cloth, Concert II, CC, Parrot CK3000 Bluetooth (Fitted by Skipton) & 2003 TDI SE, Cobalt Blue, Black Leather, Sydmeko armrest, PDC, DIS, Alu Pack, S3 Leather Gear Shift, CC, Concert II, Parrot, Performance Discs, Stealth re-map. Bought from here courtesy of Havank.
    In the Garage: 1993 Porsche 964 Celebration. Polar Silver, Big Hips

  7. #7
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    just a thought as had the pedal box apart on the bench a few months back, theres a little metal tag that pushes the plunger in on the brake light switch , i found this easily bent as very thin metal and had to bend this slightly and straightn it up to get the plunger to go fully in on the switch as brake lights were staying on when i first got a battery on the car, possibly yours needs a tweak as not quite pushing the plunger on the switch fully in.

    id also suggest popping the rear bulb holders out and checking the wiring plug and removing brake light bulbs and checking for any signs of corrosion as you say your getting bulb out warning intermittedly

    Another good thing to know is when the clutch or brake pedal is pushed the ECU drops fueling
    Last edited by JIGSAW; 16-08-2017 at 06:12 PM.

  8. #8
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    Interesting point about the metal tag on the pedal as from memory I did think mine was at an angle to the plunger and when I put the replacement in the brake lights remained on all the time meaning not enough return travel to cancel them. Before I swap I'll take a look.

    The bulb out warning is coming on nearly all the times I press the brake but they are not blown. The flickering does suggest a faulty connection or faulty pedal switch and I wonder if the occasional flickering is making DIS think there is a blown, only for when they come on as normal it then thinks its sorted? Having the loud beep everytime I go for the brakes isn't pleasant.
    At the Annexe: 2004 TDI SE (90Bhp) Mauritius Blue, 16" 5 Spoke alloys, Satellite cloth, Parrot Bluetooth
    On the Drive: 2004 TDI SE Mauritius Blue, Black cloth, Concert II, CC, Parrot CK3000 Bluetooth (Fitted by Skipton) & 2003 TDI SE, Cobalt Blue, Black Leather, Sydmeko armrest, PDC, DIS, Alu Pack, S3 Leather Gear Shift, CC, Concert II, Parrot, Performance Discs, Stealth re-map. Bought from here courtesy of Havank.
    In the Garage: 1993 Porsche 964 Celebration. Polar Silver, Big Hips

  9. #9
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    Have you tried pulling the plastic plunger on the brake switch further out.
    They self adjust and so if it is just on the verge of being on it could flicker on and off.

    Press the pedal down and grab the plunger and pull it slightly further out. When the pedal is released the plunger is pushed back in to the correct length and this might help?

    Steve B
    2003 FSI Sport in Violet Silver (LY4W), 85k miles, ex-Motorshow car 2002. Well specced, RNS-D, OSS (working) Red leather sport heated seats with 3 seat bench. Being restored to original spec

    VCDS and Key programming service Including the new shaped key fobs, Votex Jacking point covers (3d copies) available.


  10. #10
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    Steve - Yes tried that as I noticed they were on a ratchet. Again today most times I applied the brake the blown bulb illuminated with the 'alarm' and then cancelled only to repeat this at erratic intervals. Obviously when driving I'm not able to see what's going on at the back.

    I'm struggling to see it's the swicth causing the issue with the blwon bulb activating and de-activating?
    At the Annexe: 2004 TDI SE (90Bhp) Mauritius Blue, 16" 5 Spoke alloys, Satellite cloth, Parrot Bluetooth
    On the Drive: 2004 TDI SE Mauritius Blue, Black cloth, Concert II, CC, Parrot CK3000 Bluetooth (Fitted by Skipton) & 2003 TDI SE, Cobalt Blue, Black Leather, Sydmeko armrest, PDC, DIS, Alu Pack, S3 Leather Gear Shift, CC, Concert II, Parrot, Performance Discs, Stealth re-map. Bought from here courtesy of Havank.
    In the Garage: 1993 Porsche 964 Celebration. Polar Silver, Big Hips

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