1980 300sd headlight and highbeam problem

[Mirsad]

Can anyone help me with this issue?

I have a problem with the headlight and high-beam. When I turn on the high-beams my right headlight works properly with the high beam being on while the left headlight completely turns off. I checked my light bulbs in both rear and front and they seem fine. I'm wondering where I can go from here to resolve this issue.

Thanks

Mirsad

[Brian Carlton]

Replace the LF headlight.

[PaulC]

Brian gave you the executive summary. IIRC, in U.S. spec. sealed-beam quad headlight systems, the low-beam headlights have two filaments, one that is energized when the low-beams are selected, and another that is energized when all four lights are activated.

A low beam light could have one of those two filaments broken, which would cause the behavior you're experiencing.

[Mirsad]

This is the W116 chassis with two lenses in the headlight. Does it change anything about the problem?

[PaulC]

No.

Your factory headlights on your U.S. spec model are the same type of sealed beam headlights first legalized for cars sold in the U.S. since 1958.

Swiped from Wikipedia:

Headlamp styling in the United States, 1940-1983
In 1940, the US government mandated a system of two 7 in. (178 mm) round sealed beam headlamps on all vehicles. Headlamp styling in the United States virtually ceased for many decades after this event.

A system of four round lamps, rather than two—one high/low and one high-beam 5¾ in. (146 mm) sealed beam on each side—were introduced in 1952 when the Prevost Car company included them in its Citaden bus model. Cadillac, Chrysler and Nash placed them in some of their car models in states that permitted the new system for the 1957 model year, and other American marques followed suit when all states permitted quad lamps in 1958.

This lighting system was also used in some foreign cars sold in the U.S., including your Mercedes.

Your low beam headlight (the one located furthest away from the grill) has three metal prongs that plug into the wiring harness that powers the headlights. One prong serves as a ground, one prong serves as the positive terminal for one filament that lights up only when the low beams are on, the last prong serves as the positive terminal for another filament that lights up only when you activate the high beams.

In short, the low-beam headlight in your system is really two light bulbs in one. In your case, one of the filaments is broken, or you have some type of wiring/corrosion problem that is prohibiting current from flowing through that filament.

[Mirsad]

I replaced the low beam headlight but the problem is still there.

I checked the voltage on the harness when the headlights are on with the high beams. On the right side I do get the voltage for the high beams but no voltage present on the left side of the high-beams. When I turn off the high beams both harnesses have voltage on the low beams. I'm trying to think there is another problem than the low-beam headlight?