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!
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.

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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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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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......
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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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.
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
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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.


Dick Chown Award 2016
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
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?
Due to bad weather I've not had chance to swap over the siwtches between both A2s but following todays exploits I'm thinking wiring. Without touching the brake if I put the side lights on the 'blown bulb' sounds in DIS and after a while goes out. All the bulbs are good so its not a defective bulb but the car must be reading there is a bulb out and then clearing???
Id be checking and cleaning all the earth points as sounds like bad earth as intermitted , theres a how to posted somewhere , battery conections and like i mentioned before the light units themselfs, as dis is the instrument cluster itself if the earths dont fix the issue id then be removing the intrument cluster cover and checking the wiring plugs on the back incase somethings worked lose somewhere
I had this problem changed the Brakelight switch,cured it and had a flicker after so Changed both Brake light bulbs and cleared it,my fault really as I was in there months before trying to see if LED blbs would work.
worth trying to remove any ambiguity


Dick Chown Award 2016

My money is on it being the rear light cluster, bad contacts in the bulb holder or loose wiring, but probably the former.

Steve B

Well after swapping brake switches over from one A2 to the other, taking apart the LED high level brake light, checking all the joints/earth straps on the wiring/connectors it all came down to a defective bulb in the NS unit.

For some reason the bulb internals had gone defective and would occasionally flicker both filaments. Most noticeable when I put the side lights on and the high level brake light and NS brake light would flicker without the brakes being on. I suspect the LED being quicker to illuminate drew me in that direction.

The moral of the story is, check and change out the bulbs first even if they look OK!
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