Hi All,

I have a 1990 500 SL I purchased 2 years ago. This problem has persisted
as long as I have owned the vehicle. I am referring to one passenger side rear tail light socket only. I have received several warnings
about driving at night without the proper tailights working.

My problem is that when I turn on my headlights, only one rear marker light (passenger side) comes on, (the far outside one). The third light socket from the right, does not.

I also get the "lightbulb Out" idiot light on the dashboard.

I have checked the following:

The light bulb.
The wiring and harness, it looks brand new, connectors are fine.
The bulb connections and contacts are all clean and new looking.
The headlight switch appears to be working properly without incident.

I did notice however, that the socket in question,(passenger side, third from right) had only one electrical contact that connects with the bulb in question (white wire).

The same socket on the drivers side tail light bulb panel, has two contacts in the same socket, a white wire and a black wire (ground?) that is wired to a connector and a very small black box that is mounted on the bulb panel.

My Question is:

Is this the correct wiring configuration for the bulb panels? The drivers side bulb socket is grounded and the passenger side identical bulb socket is not?

Could the "headlight switch" be to blame?

Could a missing ground wire from the passenger side bulb socket panel be the problem? and if so are these parts available, or will I have to
purchase an entire bulb socket panel assembly?

Any help at all will be greatly appreciated.

Thanks to all responding for their support.

Best Regards,

Ken