Bulb warning light

maprice · Oct 8th, 2005, 22:15

Hello,
My 98 TDi briefly flashes the bulb warning light intermitently for a fraction of a second when the brake peddle is pushed. I am sure it did not used to do this and is becoming annoying. Does anybody know what is causing this to happen.

Thanks

Mark

adieu · Oct 8th, 2005, 22:23

Blown brake light bulb?

imac · Oct 9th, 2005, 18:23

>Blown brake light bulb?

Mine comes on occasionally (once today, last time was 3 weeks ago) for a few miles, every time I brake. Then it dissapears for a few weeks - I've checked, and all brake lights are working as they should. I'm thinking possibly a loose/dodgy bulb or connection.

burchi · Oct 9th, 2005, 19:11

Hi Mark

When I had my 850 T5 (1995), I used to get this problem and it seemed to be like an early warning the bulb was on it's way. As all the bulbs appeared to be working, I just changed both brake light bulbs (very cheap) and the problem never re-appeared. It may also be worth cleaning up the contacts where the bulb sits just to be sure.

Traduk · Oct 10th, 2005, 11:32

I have had this problem on an intermittent basis for three years.

There is a small box located in the rear of the car which operates like a form of Wheatstone bridge and uses both brake light bulbs as part of the circuits. If both bulbs light simultaneously then two reed relays operate simultaneously and no signal is sent to the bulb failure light (in the dash).

If one reed is fractionally slower than the other then the bulb failure light will flash for as long as it takes the slowest one to operate (milliseconds). The cause for one reed being slower than the other can be mis-matched bulbs (it is important that they are reaplaced in pairs from the same manufacturer), one bulb reaching near failure point, high resistance connections, poor battery voltage levels or unlikely but the detector unit itself.

I had my detector unit changed with a known good one and the problems did not change. After a subsequent battery failure it went away for months but returns from time to time. IMO the detector is somewhat over complicated and for all it's cleverness failed to detect a real brake light failure that I had. One of my bulbs went short circuit, blew the fuse and because the detector uses the same supply it failed to illuminate the bulb failure light.

sholtby · Oct 10th, 2005, 17:01

The brakelight bulb holder is making a poor connection with the bulb. Clean the contacts with some fine sandpaper and bend them slightly so they make a better connection.

Simon

Oct 12th, 2005, 19:54

Hi Guys, this has happened to me just recently. Change the brake light switch on the pedal! I had the same symptoms for about 3 months and couldnt figure out why the light flickered when I pressed the brake pedal. My brake lights went altogether a couple of weeks ago and I only found out by looking in a shop window as I was stopped at traffic lights (phew). I got a new switch and hey presto no more flickering light! The old switch was really charred and black when I looked inside! I had tried cleaning the bulb contacts, changing the bulbs and cecking for loose wires to no avail!

Hope this helps,

Jase.

Oct 8th, 2005, 22:15	#1
maprice New Member Last Online: Jun 15th, 2013 17:22 Join Date: Dec 2002 Location: Malvern	Bulb warning light Hello, My 98 TDi briefly flashes the bulb warning light intermitently for a fraction of a second when the brake peddle is pushed. I am sure it did not used to do this and is becoming annoying. Does anybody know what is causing this to happen. Thanks Mark

Oct 8th, 2005, 22:23	#2
adieu Master Member Last Online: Feb 5th, 2021 19:07 Join Date: Dec 2002 Location: swindon	RE: Bulb warning light Blown brake light bulb? __________________ Speed has never killed anyone, suddenly becoming stationary… That’s what gets you. A turbo: Exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster

Oct 9th, 2005, 18:23	#3
imac Premier Member Last Online: Sep 19th, 2009 21:23 Join Date: Nov 2003 Location: Hove, Actually.	RE: Bulb warning light >Blown brake light bulb? Mine comes on occasionally (once today, last time was 3 weeks ago) for a few miles, every time I brake. Then it dissapears for a few weeks - I've checked, and all brake lights are working as they should. I'm thinking possibly a loose/dodgy bulb or connection. __________________ MY97 S70 T5 CD - Now with added Milltek!

Oct 9th, 2005, 19:11	#4
burchi Senior Member Last Online: Nov 29th, 2022 21:37 Join Date: Dec 2002 Location: Storrington, West Sussex	RE: Bulb warning light Hi Mark When I had my 850 T5 (1995), I used to get this problem and it seemed to be like an early warning the bulb was on it's way. As all the bulbs appeared to be working, I just changed both brake light bulbs (very cheap) and the problem never re-appeared. It may also be worth cleaning up the contacts where the bulb sits just to be sure. __________________ Ian Burch 2003 ('53 reg) V70 R Manual. Ferrita 3" Downpipe & Sport CAT, HEICO Sport Exhaust with Quad Tips! Sold but not forgotten.... 1998 Saffron V70 R AWD Manual RICA 310 Chip, SAMCO Hoses, S/Steel Exhaust with 2 x 4" Outlets, OEM Strut Brace, Dynaudio Premium Upgrade, K&N Panel Filter

Oct 10th, 2005, 11:32	#5
Traduk Member Last Online: Sep 15th, 2014 11:10 Join Date: Oct 2002 Location: Surrey	RE: Bulb warning light I have had this problem on an intermittent basis for three years. There is a small box located in the rear of the car which operates like a form of Wheatstone bridge and uses both brake light bulbs as part of the circuits. If both bulbs light simultaneously then two reed relays operate simultaneously and no signal is sent to the bulb failure light (in the dash). If one reed is fractionally slower than the other then the bulb failure light will flash for as long as it takes the slowest one to operate (milliseconds). The cause for one reed being slower than the other can be mis-matched bulbs (it is important that they are reaplaced in pairs from the same manufacturer), one bulb reaching near failure point, high resistance connections, poor battery voltage levels or unlikely but the detector unit itself. I had my detector unit changed with a known good one and the problems did not change. After a subsequent battery failure it went away for months but returns from time to time. IMO the detector is somewhat over complicated and for all it's cleverness failed to detect a real brake light failure that I had. One of my bulbs went short circuit, blew the fuse and because the detector uses the same supply it failed to illuminate the bulb failure light.

Oct 10th, 2005, 17:01	#6
sholtby Premier Member Last Online: May 26th, 2010 20:17 Join Date: Dec 2002 Location: north east	RE: Bulb warning light The brakelight bulb holder is making a poor connection with the bulb. Clean the contacts with some fine sandpaper and bend them slightly so they make a better connection. Simon

Oct 12th, 2005, 19:54	#7
suck-it-and-see Guest Location:	RE: Bulb warning light Hi Guys, this has happened to me just recently. Change the brake light switch on the pedal! I had the same symptoms for about 3 months and couldnt figure out why the light flickered when I pressed the brake pedal. My brake lights went altogether a couple of weeks ago and I only found out by looking in a shop window as I was stopped at traffic lights (phew). I got a new switch and hey presto no more flickering light! The old switch was really charred and black when I looked inside! I had tried cleaning the bulb contacts, changing the bulbs and cecking for loose wires to no avail! Hope this helps, Jase.

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