The problem has been going on for years.

First symptom upon starting the lamp defective message would come on. Upon very careful inspection ALL bulbs are lit! When I press the "R" button I would get the temperature , mileage and clock back and the Lamp Defective message would not return, even after hours of driving. Upon restarting the car everything would be normal the Lamp Defective would not be lit.

Recently the Lamp Defective always comes on at a start. All bulbs are lit and have been replaced numerous times the license plate bulbs light work and have not been replaced.

Now the Lamp Defective light comes on at start and after hitting the "R" button the Lamp Defective will go out and come back on sometimes within a second or two, always within a minute or two. The Lamp Defective will come on while driving without touching the brake, turn signals or anything. It comes on simply while driving. It appears to be vibration oriented?? It will come on while sitting at a stoplight for several seconds. It does not come on upon initial brake application but sever, even 15 to 20 seconds later but not always.

The rear driving lights have the dreaded melted plastic and I have tried the bending and tinfoil fix and finally hard wired a bulb base into the taillight so I am confident they are making good contact.

I have read somewhere that there is a cold soldered joint in the headlight light switch. It is a pucker job, but I removed the switch opened it up and re soldered the obvious connections. Good news in that I didn't screw anything up. Bad news in that it fixed nothing!

Is it time to replace the headlight switch? Are salvaged switches OK? My bad in that I did not record a part number for the light switch.

Ideas please.

__________________
1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250

Interested in watching this thread. My '98 E300 bulb warning light comes on too and I don't see anything wrong. I know of one other one that does the same thing.

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Jim

I have had a few legitamate warnings for bulbs that failed but I have had a couple ghost warnings as well.

From the owners manual:
"Exterior Lamp Failure Indicator
When the symbol and message appear after starting the engine, or if it comes on while driving, this symbol indicates a failure in the parking lamp, taillamps, stop lamp, or low beam headlamp.
If an exterior lamp fails, the indicator symbol will come on only when that lamp is switched on.
If a brake lamp fails, the lamp failure indicator will come on when applying the brake and stays on until the engine is turned off."

What happens when you don't acknowledge the alarm with the R button, does it go away on its own? It appears from the description that the brake light alarm is latching and the other light alarms are self resetting.

However if you acknowledge it then the "two squares" icon appears and the warning persists until the car is shut down, at which time it reappears.

I am wondering if this would help to narrow down the problem.

I had one like that on my W124, that was intermittent, it was a pain trying to catch it in the act. At least on the 124 you just get one idiot light and no annoying beeper.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

I know that the w124 had some sort of large plug-in module near or in the fuse box under the hood that was in charge of all the light circuits that ran to the light failure bulb. It has a bunch of resistors or something in it and if one of them fails or senses less than the required voltage, it trips the light in the dash and also extinguishes that particular bulb. I went through maybe 4 or 5 of those things because each one was showing different lights to be out. First one was a rear side marker light, another was a fog light I believe, another was the front corner light. I jus kept putting used modules in at the junk yard til I found one that wouldn't trip any of the circuits. Yes, it's annoying.

I owned a '99 from new until 2011. For most of that time, bulb failure was indicated. One problem turned out to be the wiring harness for the left fog lamp, which rotted away. But then it came on again and I couldn't find a problem. I'm usually good with electrical stuff, but never solved this one.

I always use the R button, I will try it without the R button.

I am also good at electrical but getting frustrated.

I have a bit of an intuitive feeling it might be my right marker light, it was difficult to seat the bulb but it did seat and light. I may remove the wheel liner and try jiggling the wires to see what happens.

__________________
1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250

No help, but those 99 E300s will make you crazy what with the lamp indicator light. I was rather fortunate with mine.

I will say this, my RT rear lamp assy. went bad, and that was about a $300.00 bill at the MB dealer R&Ring it. How did the meltdown occur? By using a bulb I bought at a retail auto parts seller. I learned to buy ALL replacement bulbs from the MB dealer from then on.

Very important: ONLY buy bulbs from your MB dealer, NOT NAPA or PepBoys or AutoZone, or O'Reilly - I learned the hard way not to buy other than genuine MB dealer supplied bulbs!

My Brother that now owns the '99 E300 still has the ASR / BAS lamp illumination that may have something to do with the vibrating, loose front rt wheel bearing - according to an ex-MB dealer tech. he visits with at his tire shop.

EDSBO - not trying to be critical, but you might want to upgrade out of the W210 MB diesel to a W211 05/06 I6 CDI sedan? The W211 fits my size body in more comfort in the driver's seat, than the W210 - FWIW.

I decided to avoid the V6 configured E320 W211s manufactured from 07 to 09, because of the V6 and it's $2K to fix oil-cooler leaking issue that they develop. Besides - they're basically the same car in the 05 and 06 CDI. - 0.02.....

I had an issue with the ABS light and warning light not long ago... sometimes like you, as soon as I started the car, bang, the warning was kicking in... Oh the pain...
I disassemble the rear tail lights, nothing. The entire gear selector to look at the reversing light switch... Nothing... but a real pain to put it back together...
Looked everywhere... Nothing...
Then I changed the brake switch and things started to get better... But after a short while, same, light warning coming in. Arghhh!!!
I finally find out it was a fuse in the cabin that was not connecting properly... The fuse was OK but a little corroded and I can only guess the connections inside the module would have been the same.
After wiggling the new fuse in and a bit of WD40 on the fuse all is bak to normal and I never had the light warning again.
Might want to try that?

__________________
E300TD year 2000. RUSTY SOLD
cost a fortune to maintain on the road
but run well on WVO
Second Merc died due to corrosion ( NOT rust) How can mercedes get away with that for so long?
Third lasted a month then went away...
Fourth now... Corroded too...

In the W124 the lamp failure is the huge relay in the back of the fuse box. And about 1/2 the fuses in the fuse box are lighting circuits.

In the W210 the lamp failure is part of the light switch. And the fuses for the lights are in the side of the light switch, which is accessed from the sail panel on the drivers side.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

My bro's W210 has been indicating bulb failure, inspected the car and found that his right little tiny orange bumper indicator light was out. So it does work.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Yup that one got me too. It checks *every* bulb on the exterior of the car.

The worst are the little H6 "city" lights in the smaller "eyes" in the front of the car. Those are hard to find except at the dealer and they are like $15 each.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Most replacements I have done have been the taillights melted, the harness for the parking lights became deteriorated, and in a lot fewer cases the headlight switch. I'm most certain is not related to your headlight switch.

Remember that the rear taillight fix you did is nothing more than a bandaid. More important that you replace the rear taillights and do it correct. Right below the speaker on the driver side of the dash, is a myriad of fuses. It would be wise in your case to check as much of the simple things before going out and replacing parts that you are unsure of the function.

A similar situation I went thru with my personal car, '99 E300 around three years ago was I was getting a lamp defective light for a bit. Just like in your case, no lights were out. It was indeed the harness for the parking lights. Absolutely worth checking. Now that this issue is more known as these cars have aged, I check them when I replace the bulbs to inspect the condition.

A few things.

Make sure the bulbs are the exact trade number / wattage as original. Any name brand bulb is fine as long as it is the correct wattage and meets trade design specs. From the systems I've seen that test bulbs when they are on, the module is looking for a specific current flow then decides if the bulbs are working. If current flow is low the warning will light up even if the bulb is lit. They might also look at too high current flow and trip a light.

Any corrosion in connectors / sockets is going to reduce current flow. If you have a failing ground, all sorts if strange behavior will occur also.

If you have a system that tests bulbs without turning them on, I have not researched how they work.

Electronic components start to go off spec. Electrolytic capacitors dry out and fail causing all sorts of odd behavior.

Bulbs wear out before they burn out. The filament starts to loose tungsten and gets progressively thinner, I haven't checked resistance but I'd expect it to go up as the bulb ages. Also, a filament can have a break, the broken strand will flop about and sometimes reattach allowing the bulb to light up again.

I respect your opinions and have considered moving up to an even newer model but like you found a few deal killers. The oil cooler in the middle of the "V" requiring everything up there including I believe the turbo to be removed. I have heard that it is uncertain whether the fix will be temporary or whether it will have to be done regularly.

Have alos read about a "black death" where combustion gasses blow by the injector threads, erode the head and you then require a new head at even greater expense.

I have also heard rumours about balancing shafts regularly going out destroying the engine. I have not perused this as the previous two defects run $4,000 to $6,000 or more and thus are deal killers.

2005 or 2006 are very tempting. 2007 and newer could be trouble on top of trouble

A good tip but I have already taken each fuse out from the light switch which is accessible from the drivers side of the dash with the access pane removed.

I removed them, hit them with a shot of Caig DetoxIT D5 and cleaned them with a paper towel. They all looked good but I am trying to eliminate everything possible.

Can you be a bit more specific please?

Tonight I removed the passenger's side inner wheel well liner and checked the side marker which I am suspect of but could only get the Light Defective once and it just may have been random, couldn't get it to go on again once reset.

I also took the covers off of the back of both head headlights and all connections look good, no burning, discoloration and everything looks secure.

The tabs have always been broken off the H6W bulb holders and I use a bit of foam rubber to hold them in place once the covers are re-latched.

I am close to replacing all bulbs again with matching pairs.

For additional information some times when the Light Defective meaasge first comes on and I hit the R button it immediately, within a second comes back and I can hot it 7 or 8 times in as many seconds and have the warning come back. Yet, when I stop the car and do a walk around all are lit and upon hitting the R it will stay off.

__________________
1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250

EDBSO:
If the 05/06 CDI weren't a better car, I'd of never upgraded to it.

I have NO interest in the V6 configuration '07-'09 E320 Bluetecs because of the V6 configuration. I dodged a bullet avoiding them. Besides - the 05/06 CDIs are way less $. For IMO a better car.

I was on top of the issues my W210 '99 E300 presented. I just wanted something newer, hence the CDI sedan.

With ALL the helpful hints and experience here - I am going to FWD this ALL to my Brother that now owns my '99 E300.

Great thread/ideas, EDBSO. Ya'll keep the information coming on the W210s!