Lights Out !?? - PeachParts Mercedes-Benz Forum

Bryan Harter · #1 10-11-2003, 11:00 AM

I noticed a problem recently that started a month ago on my 1992 500E. Let me describe what I have found and see if any W124 owners have had the same experience.

The Lamp Out indicator on the dash came on when I would back up and hit my brakes....So I didn't worry about it for a while.
I have the car interior removed except drivers seat but have not touched any wiring and only drive it for specific reasons, such as to take it to the dealer yesterday.

I did finally check it and found all brake lights (corners and center)
seem to work fine. Reverse lights also both work fine....

Last night I noticed the Left headlight, L running light, L tail light did not work. I checked the fuses, they seem to be OK, even took them out.

Turn signals (f/r) work.

I next turned on just the running lamps. Right side was OK, Left front was off, left tail was off, left rear corner was on.
I took out the tail lamp assy. on both sides and noticed a faint glow to the right rear brake light.

Could it be the switch on the dash going bad?

Thanks for any advice.

Gilly · #2 10-11-2003, 05:18 PM

Bryan
I doubt it's the light switch. When you have a lamp failure system like on these cars, the light switch just signals a control module what to turn on, and the control module monitors the individual bulbs to see if there is a failure or not. So if you turn on the parking lights for example, the control module turns on just the parking lights. it sounds possibly like it's a bad lamp control module, but I'd get some testing done before ordering anything that expensive. The module is in the rear part of the fuse box, you need to take some screws out to get to it (on the way rear part of the fusebox, behind all the fuses).

Gilly

Bryan Harter · #3 10-11-2003, 05:33 PM

Thanks Gilly !

I haven't pulled the wiring schematics out yet but was going to pop the cover off that box and do some simple voltage checks at the fuses.

Gilly · #4 10-11-2003, 05:48 PM

Check fuse 8 real close.

On the headlight, can you look at the bulb itself? Maybe try swapping side to side? If the headlight is still inop, also see if it's low beam out, or high beam, or both?

Gilly

aldedmon · #5 10-23-2003, 02:22 AM

Bryan, That's just freaky. My light out indicator is on as well. Mine comes on whenever I hit the brakes ONLY. I switched out all the rear bulbs with those in my 400E and it still persists. Let me know if/when you find a cure

neileg · #6 10-23-2003, 04:55 AM

Whenever you get odd light interactions like this it is worth checking the grounds at the light assembly.

AF300E · #7 10-23-2003, 07:35 AM

Mine has the same thing, 1988 300E, euro lights.
Had Front end work done including headlight replacement (not by me) and the globe warning light has been on ever since. Have replaced all parker globes since it comes on when the parkers are switched on. The "authorised" bodyshop that did the work have no clues whatsoever, I seem to know more about MB's than they do. They told me to take it to an authorised workshop since "they will have a computer to diagnose the problem".
I told them that there is no such thing as a computer for this car that will diagnose that problem (I know the impulse counter intimately) but they swear that such a computer exists.
How do these workshops become authorised? Does the authorisation process involve a box of weeties and the extrication of the authority from therein?

Anyway, I will fix this problem, i suspect they have blown a relay for me when they were replacing the headlight assemblies.

Those years in service reception etc have taught me well how to deal with issues such as these.

Bryan Harter · #8 10-23-2003, 11:25 AM

OK -
Found the problems.....

Light Switch at the dash had a bad spot on it, $60...

One more thing...bad bulbs...probably taken out due to
a problem...Left H4 and Right H3 (fog)....I had 130W H3's
in it, may have been part of the problem....I am backing down
to Osram +50's. Have been running Hella +30 H1 & H4.

Also the grounds were corroded on the taillight assembly.
I think the body shop probably bumped something loose
in the process of removing the rear valence while working
on my paint and that seemed to start it.

Use another wire to create a good ground and ground out the assembly. If that fixes it, pull the metal strips, clean everything with a bit of emery cloth and put some electrical (silicone) grease
on things.

G-Benz · #9 10-23-2003, 12:00 PM

90% of the time it's the metal strips in the taillight housings.

They loosen over time and create gound faults that set off the lamp indicator even if the bulbs are okay. Pressing them back into place solves the problem for good.

Usually the metal track that houses the brake light is the culprit. So most will start a thread about the problem stating that pressing the brake pedal sets off the indicator.

Another common symptom is when you switch on the headlights after starting the car and press the brake pedal, all of the illuminated switches in the car rapidly flash on and off!

Hope this ends some grief to those of you who have been perplexed by this issue...

Bryan Harter · #10 10-23-2003, 12:19 PM

I had suspected the strips to be loose when I opened it up.
Sure enough there was one strip that had come loose from the plastic clips that hold it....snapping it back in did not fix the problem! The confused me, but the two bulbs going bad really threw me off course. I was suspecting the light controller....thankfully it was only the switch.

G-Benz · #11 10-23-2003, 01:37 PM

Quote:

Originally posted by Bryan Harter
I had suspected the strips to be loose when I opened it up.
Sure enough there was one strip that had come loose from the plastic clips that hold it....snapping it back in did not fix the problem! The confused me, but the two bulbs going bad really threw me off course. I was suspecting the light controller....thankfully it was only the switch.

Like I said, 90% of the time, this is the issue.

Someone else here had solved their problem when the dealer replaced the switch. So I had bought a new switch as well, only have the problem persist. Only after discovering the metal strip issue did the problem go away.

I have an NOS W124 headlight switch if anyone is interested?