Brake lights and tail lights together

M

Merlin

Member
Weird one this: I had a problem with a tail light and EPC recently and changed the brake pedal switch.

I’ve done something wrong though because the tail lights and brake lights operate at exactly the same time. When I turn the lights on, the brake lights also activate (including the LED in the window) and when I press the brake, the tail lights and brake lights activate, even when headlights are off (I discovered this when I was driving in daylight and the dashboard lighting changed every time I pressed the brakes). EPC light is on, too.

The bulbs in the rear lights are dual filament. I read elsewhere on here that they can be incorrectly fitted but I’m not sure how. And if it were the tail light bulbs, why would the LED brake light be affected too?


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Try taking both the bulbs out and see if the central LED brake light still comes on with the headlight switch. Look at the bulbs and the holders, the bayonet pegs have to align correctly and it may be possible to fit them so the 2 contacts on the bulb ends bridge the 2 contacts on the holder, connecting the 2 circuits. Best of luck


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Evening,

If what you’re experiencing was the case prior to the switch swap and you’ve not been anywhere near the rear light boards the. I would presume that nothing is wrong back there.

It’s definitely worth checking the condition of the wires entering the connector to the switch you swapped. Logic says it can only be that or the brake switch fitted is not quite what it’s supposed to be, is it a genuine part from Audi or an aftermarket part from ECP/AutoDoc or similar.

Kind regards,

Tom
 
BiggDogg said:
Try taking both the bulbs out and see if the central LED brake light still comes on with the headlight switch. Look at the bulbs and the holders, the bayonet pegs have to align correctly and it may be possible to fit them so the 2 contacts on the bulb ends bridge the 2 contacts on the holder, connecting the 2 circuits. Best of luck


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Click to expand...

When I take both bulbs out about 1/4 of the rear LED light comes on with the headlight switch.


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2work said:
Evening,

If what you’re experiencing was the case prior to the switch swap and you’ve not been anywhere near the rear light boards the. I would presume that nothing is wrong back there.

It’s definitely worth checking the condition of the wires entering the connector to the switch you swapped. Logic says it can only be that or the brake switch fitted is not quite what it’s supposed to be, is it a genuine part from Audi or an aftermarket part from ECP/AutoDoc or similar.

Kind regards,

Tom
Click to expand...

I got it from GSF
64cbbd3050196919d39fb55e13b9ec9d.jpg



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Half the LEDs? That is weird. Does the car have a tow bar (or wiring for one) fitted? This sounds like a problem with wiring or one of the bulb holder assemblies, contacts bent out of shape maybe. That’s the only other thing that springs to mind. I’ll dig out my wiring diagrams.


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BiggDogg said:
Half the LEDs? That is weird. Does the car have a tow bar (or wiring for one) fitted? This sounds like a problem with wiring or one of the bulb holder assemblies, contacts bent out of shape maybe. That’s the only other thing that springs to mind. I’ll dig out my wiring diagrams.


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Click to expand...

Not even half - more like a quarter on the left. No tow bar. I’ll have a good look at the bulb assemblies in daylight and try new bulbs.


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My money is on incorrectly fitted dual filament bulbs shorting. If they were forced in the wrong way around the connectors may now also be damaged.
 
audifan said:
My money is on incorrectly fitted dual filament bulbs shorting. If they were forced in the wrong way around the connectors may now also be damaged.
Click to expand...

Can anyone provide a link to bulbs that are guaranteed to fit? There seems to be some confusion about which ones do, and I’m not sure which model of bulb was factory fitted?


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The bulbs are P21 5W bayonet fitting and are pretty universal. Try to avoid ones with very soft or little solder on the contacts.

Here is a suitable example on ebay. Not to say you can not obtain similar from a local parts factor / Halfords or even dealer...

www.ebay.co.uk

2 x Lucas 380 P21/5W BAY15D Brake Stop & Tail Light Car Bulbs LLB380 12v 21/5w | eBay

Base: BAY15D. 380 P21/5W 12v 21/5w Bulb. Part No: 380. To Fit: Brake & Tail. CAR SPARES DIRECT. Pins: Direct opposite each other, one higher than the other. Watts: 21/5W.
www.ebay.co.uk

This makes the side light 5W and the stop light 21W.
 
audifan said:
The bulbs are P21 5W bayonet fitting and are pretty universal. Try to avoid ones with very soft or little solder on the contacts.

Here is a suitable example on ebay. Not to say you can not obtain similar from a local parts factor / Halfords or even dealer...

www.ebay.co.uk

2 x Lucas 380 P21/5W BAY15D Brake Stop & Tail Light Car Bulbs LLB380 12v 21/5w | eBay

Base: BAY15D. 380 P21/5W 12v 21/5w Bulb. Part No: 380. To Fit: Brake & Tail. CAR SPARES DIRECT. Pins: Direct opposite each other, one higher than the other. Watts: 21/5W.
www.ebay.co.uk

This makes the side light 5W and the stop light 21W.
Click to expand...

Seems to be known as a 380 bulb.


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Ok so seems like a fairly standard dual filament bayonet bulb. I thought I’d read on another post that you had to use a very specific one. I’ll report back when I have done some investigation in daylight and tried new bulbs. Thank you all for your help so far.


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Merlin said:
Ok so seems like a fairly standard dual filament bayonet bulb. I thought I’d read on another post that you had to use a very specific one. I’ll report back when I have done some investigation in daylight and tried new bulbs. Thank you all for your help so far.


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Click to expand...
Go to Halfords and use the bulb/filament order menu… you will see one near the bulbs… used one recently as I had similar problem. Turned out to be brake switch. I removed brake switch from other A2 as I knew this was working and it was the solution as everything was okay after swapping said switch.
 
Hi All. Ok have resolved it and as so many have pointed out, it was the bulbs. At some point someone (me?) put the wrong bulbs in the brake/tail light holder. Have replaced with 12v P21/5W bulbs. It’s easy to confuse them - the wrong bulbs looked similar except that the securing nubs on each side are at the same height on the barrel; on the correct bulbs they are at different heights so can only go in one way. Incidentally, even with the correct bulbs i put one in wrong at first - you can push them in too far; when properly fitted there should be about 50mm of the bulb barrel clear of the fitting.

Am I right in saying there is only one rear fog light on the driver’s side? If so then all is working correctly.

Still have the EPC light on the dashboard; I’ll see if it clears when it goes into the garage for a once over before the MOT.

Thank you all for your advice.

Here a photo of the correct bulbs:
5a2ef4b53404dd8a73d0494978726b1d.jpg



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Yes, as supplied from the factory, A2's only have the one fog light, on the same side as the driver. The bulb holder and connection points are present on the other side however, so it's easy to run a wire across to give yourself a second foglight if you wish. There will be several on here - if not many - who have done that.
 
The rear light clusters are all capable of having the fog light working but Audi only fitted the live feed wire onto the drivers side unit for whatever market. Therefore all that is needed is a correct bulb and to spur off the working fog lamp supply wire and run this wire along the bottom of the internal boot trim ( remove it and the wire can be neatly taped to the wiring loom ) and up into the non working side and and connected to the fog light tract or main wiring plug. and routing the wire neatly off to the side.

Twin fog lights and twin boot lights are both very useful upgrades.
 
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