Audi A4 (1995 - 2000) - 98 Avant 2.5tdi brake light warning light on | Technical matters | Back Room Forum

Thu 27 Dec 2007 11:22

98 Avant 2.5tdi brake light warning light on - graze

I wonder if anyone can help me with this - it's a long standing problem, the brake light warning light is on all the time although occasionally for no apparent reason it goes off for a few seconds and then comes on again even though the brake lights work normally. I have changed the brake light bulbs and cleaned all the contacts and all the LCD bulbs in the window light are working too. Any suggestions much appreciated.

Edited by Dynamic Dave on 27/12/2007 at 21:00

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Thu 27 Dec 2007 11:35

A4 Avant 2.5tdi brake light warning light on - Peter D

How about a faulty handbrake switch. Regards Peter

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Thu 27 Dec 2007 13:00

A4 Avant 2.5tdi brake light warning light on - Screwloose

There are a number of different brake warnings lights. Bulb-failure? Pad wear? Fluid low? ABS fault?

Which one do you have?

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Fri 28 Dec 2007 15:13

A4 Avant 2.5tdi brake light warning light on - graze

Thanks for replying Screwloose - it's the bulb failure light - this is what makes it so difficult to work out as all the bulbs work correctly inc. the lcd in the rear window. I did get an Audi specialist to do a check a long time ago and they came up with brake light switch on the brake pedal and this was replaced but made no difference. After that i had another specialist try again and they told me i needed a new ecu [probably]. I didn't have much confidence in that analysis. There are no other faults and no other warnings about faults.

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Fri 28 Dec 2007 17:16

A4 Avant 2.5tdi brake light warning light on - Screwloose

Some bulb-failure monitoring systems don't like cheap bulbs.

I think you're a little too early to have the pulse-controlled half-power side/brake light set-up that appeared on the later A4s; but it's still worth checking that the bilbs are the right ones.

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Sat 29 Dec 2007 10:56

A4 Avant 2.5tdi brake light warning light on - graze

Thanks for that - do you mean that just in case I should change the side light bulbs as well as the brake light ones? The brake light ones are cheap ones. The car is Oct '98.

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Sat 29 Dec 2007 12:36

A4 Avant 2.5tdi brake light warning light on - Screwloose

The later, '01-on, A4 used a weird set-up where it lit up the brake-light bulb at half-power as a supplementary sidelight. I don't think that yours has that system.

Try some good bulbs - Osram etc. There are so many cheap, rubbish, bulbs around now, that you may have to get them from a dealers.

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Sat 29 Dec 2007 15:18

A4 Avant 2.5tdi brake light warning light on - graze

Thanks very much for that - no, I'm pretty certain I don't have that system. I'll change the bulbs with some from the dealer.

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