Tail Lamp Inoperative- Bad Ground?
 

My lower left rear lamp has stopped functioning. The bulb is fine, so I am guessing the problem may be a bad ground, but where to begin searching? Has anyone else had the same specific issue, or a good place to begin looking?

Thanks!

These are infamous for problems with the bulb holder contacts and there is a lot of info about a couple of methods on how to repair posted here.

I have the same ongoing problem and have found it it to be a bad connection between bulb and pcb. I renewed the bulb holders which sorted one of the bulbs, but still have intermittent problem with the other side. On an earlier 320 of the same era I found the earth to light unit failure to be the source of the problem.

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There are a couple of different ways to go about the repair but I used the solder method, putting on a bit of acid core solder on to the contact strips has been a permanent fix for probably 10 years! ;)

That's a lot quicker than my fix. As long as the contact is good after so it stops generating heat from high resistance it should be a permanent fix.

I restored the spring contacts to factory position by adding metal screws and bending the ends to reset the height of the contact.

The solder method likely is a lower resistance contact since the factory solution is zinc plated steel which is a terrible conductor.

If i had to do again I'd do both, but it doesn't need to be back to factory. The solder bump puts the contact where the lamp expects it with a lot less work.

I've found solder on BOTH the steel/zinc plate and the small contact tabs on the bulb holders works best (longest!).

Last fall, after 21 years without issues, I used Andrew's fix when the running light wasn't working on one side (the brake light would still come on). But, I noticed both sides were humming loudly. It seemed like it was going to be an ongoing battle.

After inspection, I changed out the whole set of four for about $120 on Amazon. The third party set uses standard sockets. Plus I got lightly smoked ones which look more modern to me.

I have yet to see a set of aftermarket tail lights that are correctly configured (wired) for the LCI cars (and I have looked...). They may exist, but I have yet to see any...

Be aware that the LCI tail lights are wired differently from pre-facelifts tail lights and use different bulbs etc.

Thanks guys. I had played around with the bulb holder, cleaning the contact faces and bending them up a bit. I also found a couple other threads here, and looks like I'll be diving deeper into the tail lamp unit.

These are the ones I bought, Wayne:

https://www.amazon.com/gp/product/B07N8G4SQN

They are wired correctly for my 04 4.4i. They even included wiring and sockets for the rear fogs (though I don't have them so can't say that the wiring works for them in particular).

One of the plugs was difficult to insert... I had to bend the pins inside the connector.