Bulb warning light - but no blown bulb????

[khanie]

I keep getting a bulb warning light on the dash of my 1996 E230 even though I've checked all the bulbs/lights myself and it passed its MOT this Monday. There seems no pattern to it either - it comes on sometimes and not others and even goes off again.

I'm not really worried as all the lights work but has anyone else experienced this?

Cheers

Mark.

 

[Blobcat]

Quite/very common in 210's. It is a poor connection in the bulb/bulb holders that is causing the warning light, usually one of the four rear lights.
A temporary fix is to take out the bulb holder, remove the bulb then clean the contacts on the bulb and the bulb holder with very fine emery paper. This should fix it for a few months.

 

[OmniCognateNeutronRangler]

I actually had this on my W203. The bulb warning light came on but he bulb seemed to work (brake light). I replaced the bulb and never had the problem again so I guess the bulb was faulty.

 

[eric242340]

Quite/very common in 210's. It is a poor connection in the bulb/bulb holders that is causing the warning light, usually one of the four rear lights.
A temporary fix is to take out the bulb holder, remove the bulb then clean the contacts on the bulb and the bulb holder with very fine emery paper. This should fix it for a few months.

Completely agree, and its a common problem - high resistance on one of the bulb holders. Sometimes (with all the lights on) you tap the light and it will flash, easy way to find the problomatic holder. Also a bulb with the wrong resistance can cause this.

 

[coolpot]

when mine did it once w203 i took a look at the bulb, and it had gone brown, but not blown, as eric said, i think they work on resistance, and i think as the bulb gradually gets that browney colour before they go, the buildup causes higher resistance, i left my bulb in for a bit and sure enough 2days later it blew, quite clever really, replace bulbs just before they go heheh

 

[type49]

The warning light only comes on when the faulty bulb is switch on. In other words, if the light comes on whilst driving during the day, going forward & not indicating, it is 99% likely to be the brake lights. So, when does the warning light come on???

 

[coolpot]

oh sorry i didnt realise they are different.

On mine it says for instance brake light (left) out or something, so its prob a different system to yours, you can prob ignore what i said lol

 

[type49]

oh sorry i didnt realise they are different.

On mine it says for instance brake light (left) out or something, so its prob a different system to yours, you can prob ignore what i said lol

203s are a bit more advanced & will even substitute another bulb if ness.

 

[television]

All of these system use a current sensing amp circuit,these are cheap and cheerful, it is not possible to do it as a resistance check. Ok sure if the resistance of the bulb changes as the filerment erodes away,then the current must change. This is a very simple system.

The pictograms showing all of the lamps are much more involved as all of the lamps are wired back to the current sensor / grafics generator, but the same principles apply

Malcolm

 

[sv4]

On the W203, it doesn't substitute blown bulbs on its own, it re-routes the signal to any adjacent ones. For example, if the rear right brake light has gone, it will re-route to the rear right indicator and vice versa.

On a few occasions, I had the blown light fault coming on the dash, but sorted it out by merely retightening the bulb.

 

[Glenn Smith]

I keep getting a bulb warning light on the dash of my 1996 E230 even though I've checked all the bulbs/lights myself and it passed its MOT this Monday. There seems no pattern to it either - it comes on sometimes and not others and even goes off again.

I'm not really worried as all the lights work but has anyone else experienced this?

Cheers

Mark.

Usually caused by brake light, does it ever come on if your lights are not on? if so it can only be a brake light bulb with a dicky filament, also check holders for corrosion. if it comes on with lights on give the lights a tap to check for faulty filaments (sometimes they make and brake)