Something as simple as a tail light
 

The 1990 300E 2.6 has a wiring problem

The tail light on the right side does not work. And the 'Light bulb fault light' is on on the dashboard.

• Replaced the bulb - still doesn't work
• Fuses all good, but rotated all - still didn't work
• Brushed the socket clean - still doesn't work
• Took the light panel from the right side, and plugged it in the left side - The light worked.
• Traded Light Control Module with another car (gold) - same part number - No change. The light status (tail light and dashboard light) remained the same with the Light module switched between cars. The Gold car lights worked fine with the module from the black car.
• I hunted down the wire, and confirmed with a wire diagram - the wire from the light module to the light bulb socket is GR/RD (gray with red line). I tested resistance on the line - it showed 3 ohms, which seemed like a lot. But it showed connectivity - so I figured the worse would be a dull, but functional light.

I need a creative approach.

What else should I test.

Would the Gray/Red wire at the tail light be the same Gray/Red in the fuse box area? Or could there be more than one wire that's gray with red stripe?

Thanks for the help.

It will not pass state inspection while the tail light is out.

Another hint:
The dash board light comes on when I press the brake peddle, but all teh brake lights are working.


Why would the right tail light not light, and the

Looks like a problem with the light panel. Maybe a short at the connector. Take the connector apart.

Should be 2 tail light outputs from the control unit. Scotchlok them together as a test.
If that doesn't fix it then run a new wire from the unit back.

i had same thing happen on my 91 300e it was the contacts inside the tail light assembly i dont remember where but it was something easily fixed after taking apart the tail light assembly and cleaning or repairing the contacts chech with a meter that 12 volts is getting to the connector first with the taillights on then follow to the bulb to find where the bad connection is

Nope I believe its the headlight/bulb out indicator under the screwed down section of the fuse box. Get 1 from a bone yard as new ones cost over 200 dollars. The unit controls all lights.

Well - It's fixed! (no clue why)
 

I was headed down Gilly's suggestion - twist the wires together / run a new wire.

I was pulling this and tugging that. Removed the Light Module several times - poked around trying to figure out which wire went where - the wiring diagram I'm using shows wires from box to box - but not the details within the box.

Out of frustration, I put it all back together again. With the thought - I have an appointment at the mechanic for Monday (actually they asked for the car all week) - so I quit.

Cleaned things up, for the mechanic. (Think clean the house before the house cleaner comes). But every thing back were it belongs.

I went for a drive to but flowers (moved to low tech). When driving (on a sunny day), I noticed that the dash board light was no longer on. I know from experience - the dash board light warning light goes out if teh Light Module is loose - so I feared I had no lights.

Pulled over - got gas, and asked the attendant to look at the brake lights. - All is well sir.

Well, the headlights were working fine, and all other lights were working fine - and the stupid dashboard light is not illuminated. All dash board lights light up with the key in start - but not while driving.

I have no clue what resolved the issue.

But - I did

• Replace all the lights in the tail light area (last week)
• Removed and replaced the Light Module several times

Good luck to others reading this.

To all those that suggested things - Thank you - all suggestions were attempted.

Including the "3rd" brake light, we assume.

You should also verify both right and left brake lights are using the same bulb, preferrably a european bulb (for which the system is designed). Same with taillights.

I'd be most concerned about contact between bulb holders and the contact plate in the taillight unit. This is really the only "wear" point, as contact relies on spring action of the contacts in the bulb holder.