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1994 e320 Sedan, 168K miles
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69 Posts
Discussion Starter #1
If you have dim or intermittent tail lights, try this as well as the usual recommendations... especially before buying a new assembly.

My 1994 e320 sedan had this going on for at least two weeks... only the upper brake light was working with the brake pedal depressed, the tail lights were dim overall (for a lot longer than 2 weeks) and the tail light brake lights did not light up at all when the brake pedal was depressed. My radio light, however, went out with every press of the brake pedal when the headlights were off, but was ok with headlights on (!) Occasionally the left turn signal would slow way down and threaten to quit. Brights only work in the 'On' position, but not the 'Momentary On' position. And all the while, the 'Burned out bulb' indicator would randomly light by no pattern at all.

While trying to solve this, I had been working my way through some possible solutions... all very valid to a lighting issue.

1. I switched out old stop light bulbs for new ones. Nothing.

2. I replaced every fuse in the fusebox with new ones and cleaned receptacles. Nothing noticeable.

3. I changed out my 'Headlamp Relay' with a salvage one I got (real cheap) on ebay. Seems to have made the random weird electrical problems become consistent, and much easier to diagnose step by step.

4. My home-made diagnostic reader told me the 'Stop Lamp Switch' was faulty / non operational. I have one ordered and it's still on the way here from Autohaus Az... guess it will be my back-up now.

5. Went back into the tail light assembly to look for damaged wires and found none. When re-assembling the tail lights (and with the headlights 'On') I happened to push my thumb into one of the conductive galvanized bars that hold the lamps. When I did, all the lights in that assembly became bright, and dimmed again when I removed my thumb. I checked the other side and the same thing happened.

I unplugged the two assemblies and took them inside to work on them. Looking at the design it was obvious to see that the clips that hold that bar down and the bulbs tight to the bulb contacts underneath had weakened over the years, loosening the connections made by it. Simply, the bulbs did not snugly fit in place. They even wobbled around a bit.

To get that piece snugly installed, I added a 1 1/8" - 1 1/4" phillips head bolt and a nut to each tail light assembly where it was needed most, nearer to the turn signal side, to pull and hold the bar to the plastic assembly snugly in place. Tighten with a screwdriver while holding the nut with pliers or wrench, remember not to over tighten or you will bend the metal or crack the plastic housing. See the photos for the place to drill your holes. Picture 1, inside, where nut should live, and picture 2, outside appearance and bolt location. Be careful to avoid wires under the metal bar supplying power to bulbs... just push them aside when drilling. And no soldering required.

After making the fix, I re-installed them and all of the lamps shone bright! And the brake lights all work now! Top and bottom. When I press the brake pedal, the radio light stays on and remains constant.

My 'Burned out bulb' indicator does come on still, but now only when the headlights are switched 'On', not randomly. That, and the brights still only work in the 'On' position, but not the 'Momentary On' position. (?) Hopefully that will go smoothly, too...
 

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1989 300E 125,000 miles, 2005 Acura TL, 2011 Hyundai Elantra Limited
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201 Posts
Thanks for the information. Electrical issues are a pain to track down.
 

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Registered
1994 e320 Sedan, 168K miles
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69 Posts
Discussion Starter #4
hmmm... don't know what bolt/nut size, just used what I had laying around the house.

It does not need to be exactly like mine, though, just be sure the bolt length is short (1 1/8" - 1 1/4" long) so that it does not stick out too far to re-assemble housing. I cut the bolt I used to the perfect length when installing it... You can see in the photo it is a small nut on the bolt, maybe 1/8" - 1/4" wide at most...

good luck!
 

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1993 300D 2.5 "Elsie"
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1,246 Posts
That's similar to what I did, but you made it a bit more pretty. I used zip ties and ran then around the metal bars and through the plastic...:D I also cleaned up all the connections/terminals and spread some dialectric grease on things. No problems since.

I should add that everyone should check their tail lamp assemblies and I would probably just go ahead and do something like this. Just any method of holding the metal bars in firmly. I'm betting that almost all of them are weak are broken and having poor contact with anything in there will cause issues with the bulb out warning and other related things.
 

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