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Discussion Starter #1
Well I finally took the brute force approach to solving the Light Malfunction Annunciator/Pest.

I was having limited success cleaning the contacts on the light bulbs, the holders and even the contact surface on the conductor plate.

I determined that it was the stoplights that were the main offender. I suspect the contacts couldn't take the current or had high resistance, so I decided to create some jumpers to augment the circuit.


I haven't had the Annunciator complain for 2 months now -- so I think I can claim some degree of success.

Here's how I did it.

I soldered pigtails onto the end of the contacts in the light socket -- butt soldered, not drilled through.
The blades are a spring steel and don't drill easily, but they are tinned so it's easy to make a solid and strong butt joint ( and there isn't much space for anything else.

I tinned a pigtail with a very short stripping, and then put a dab of solder on the point of the blade that lines up with the holes I drilled in the holder. You need the short stripping to avoid a long un-insulated "neck" on your finished project - to short out.

I recommend pushing them out one at a time. Maybe it's just me - but I found them amazingly easy to get mixed up. They push out easily by depressing the locking tab and pushing them up. Remove the bulb first though. It was just easier to photograph this way.

After soldering on the pigtail, I threaded it down through the matching hole. I used a #27 drill, but anything around 3/32 or so should work.

I crimped on the fasteners afterwards.

The first version just had spade terminals at the end of the pigtails, and I drilled small holes in the conductive plate and screwed the terminals to the plate with small tapping screws ( #6 x 1/2" ). This next version has spade connectors so I can pull the holder out of the car without tools. The pigtails are long enough to change bulbs, though if you want to keep the work simpler.

Notice the marks along the edge of the holder lining up with the contacts. I found this helped with determining the exact portion of the conductor plate that matched up with the specific contact. It can get mixed up and the resultant short will eat fuses.

I drilled the holes in the plate without removing the assembly from the car, so I "submerged" my drill bit in the drill so it was less than 1/4" above the chuck face. This was done so the drill didn't suddenly fly through the plate and make unwanted holes in, say, the tail light lens, for example.
 

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Good fix. What a shame what we have to do. Send it to M/B maybe they will hire you as a consultant.
 

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Mike,when you get fed up ,some brilliant things come to mind. Congratulations. I just don't have the patience.. [:p]
 

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Very nice...let's be sure we get this one in our FAQ/DIY thread.

Thanks for the good work and for taking the time to explain it with the pictures.

Enjoy the ride,
Greg
 

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Mercedes Benz should send you more than just a thank you note for your investigation and fix. So many owner are complaining about the problem. But what has MBZ done?
 

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Discussion Starter #7
Peter Guenther - 12/5/2005 6:35 PM

Damm, someone who pursues the issue. MB would have replaced the sockets!
Peter - The sad reality is that I had a spare set of sockets to play with because I went to our local dealer and spent $27 getting 2 new sockets and 2 new bulbs thinking this would put it to bed once and for all. I also took a Dremel tool and buffed the contact area on the conductor/plate.

As you can guess - to no avail[:(!]

I suspect the contacts are under-engineered for the amperage of the stop lights, and they go up in resistance, or change shape from the heat of the current and cause the error - just my guess - but it's obviously no worse than the pencil heads in Stuttgart.

This leaves the sockets as not much more than holders for the bulbs....
 

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quick fix, at the dealer we replace the tailight assy, circuit board corroded or burnt up
sometimes its just the contacts on the socket that are bent or corroded, we'll just install a new socket
 

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Lovely fix/upgrade.
 

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Discussion Starter #10
davemisto - 12/10/2005 5:43 PM

quick fix, at the dealer we replace the tailight assy, circuit board corroded or burnt up
sometimes its just the contacts on the socket that are bent or corroded, we'll just install a new socket
Replace the tailight assembly ? Is that a bit expensive and extreme?

Then again, maybe not -- I replaced sockets and bulbs with factory units and carefully buffed the contact points on the circuit board / back board -- to no avail.

That's why this unusual approach -- to avoid replacing the assembly to only face the trouble in a few years again.

This process only takes 45 minutes or so once you figure out where you are on this.

This assembly was under-engineered. This should never happen.
 

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Lamp Warning problem solved one more time

I was having a strange Lamp Warning issue that showed up as a number of odd faults.

When I would shut my car off after running with the lights on, the lights should come on and stay on for a minute or so to light your path once you shut the door. Well in some cases only the lights on half of the car would light up when other times they all would work as normal.

Then some time later, there was a strange problem when I turned my lights on. As soon as I moved the head light switch to the first position the have just the running / parking lights on, I would get the Lamp Failure warning. When I would look at all of the lights, they were all on. It took me some time to notice that there was a delay for some of the lights to come on and by then I already got the Lamp Warning.

The last thing to happen was that the running/parking light on the drivers side would not come on until I turned on my fog lights. It was acting as if they were shorted together. If I turned all the lights on fast enough, I could avoid getting the lamp warning.

I replaced my headlight switch and all of these problems went away. The switch must have been failing over a period of time and getting worse over time. Some times the circuit would be open and other times shorted to a different contact for another light. The new switch works great and all faults including the ones after I leave the car have been corrected.
 

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I think i have the same type of problem with My passanger side break light
as soon as i step on the break the "lamp Defective " lights up on the dash. Ive tried new bulbs and socket but to no avail. when I wanted to buy a new tail light assy it was $118 bucks but no returns (on Electrical parts) the guy at the parts window said it maty be a switch? the breaks light itself works but the "Lamp Defective message stays on. any body got a clue whats up???
 

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How to fix "light malfunction"?

E320 2000 4matic, once the light malfunction comes on. The front power seats and front power windows don't function until I clear the codes or I remove the #16 fuse under the hood for the left side and the #1 fuse under the back seat for right side.

Does anyone knows how to fix that problem permanently?

PS: actually all the lights are on.

Thanks!
 

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I've had two additional stop light bulbs blow out (I tried different brands) on the left side of the wagon after the first one went. They go out immediately when I step on the brakes.

New assembly?
 

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Tom:

Before we wave the :surrender: flag, let's try two more things.

1) Use a voltmeter to measure the voltage at that left socket (when someone steps on the brake pedal) but I doubt it will be out of the ordinary (let's just to make sure). As a matter of fact, measure the right one as ell to see if there is any difference.

2) Replace the bulbs in pairs, i.e., also replace the one on the right with the same (new) one as on the left. I know this particular bulb only comes with one (metal) base. Some other bulbs come with either brass or nickel base and it is recommended not to mix the bulbs with different bases. It is worth a try, IMHO.
 

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Tom:

Before we wave the :surrender: flag, let's try two more things.

1) Use a voltmeter to measure the voltage at that left socket (when someone steps on the brake pedal) but I doubt it will be out of the ordinary (let's just to make sure). As a matter of fact, measure the right one as ell to see if there is any difference.

2) Replace the bulbs in pairs, i.e., also replace the one on the right with the same (new) one as on the left. I know this particular bulb only comes with one (metal) base. Some other bulbs come with either brass or nickel base and it is recommended not to mix the bulbs with different bases. It is worth a try, IMHO.
I accidentally tried the two bulb trick you mentioned because I wanted to save the original bulb that was still working so I put both bulbs from the new pack in but no luck. I have yet to measure the voltage. SWMBO is out of town till Sunday night. I was hoping to fix it tomorrow along with a brake job if it doesn't rain. I need to get a garage.
 

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Sigh.

These instant bulb blowouts are mysterious to me because the voltage at the socket should not be more than alternator/battery voltages.

Did the instant blowouts take place when the car was running? Just try to scratch my head. :mad:
 

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Sigh.

These instant bulb blowouts are mysterious to me because the voltage at the socket should not be more than alternator/battery voltages.

Did the instant blowouts take place when the car was running? Just try to scratch my head. :mad:
As I recall, yes, the car was running. Off to work now. See you in 10 or so hours.
 

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Now see if the bulb also blows without the car running. I am trying to blame the alternator/voltage regulator. :D

This might be possible so maybe we should also measure the alternator output voltage with the engine running.
 
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