W123 Euro Headlight Grounding Problems
 

Hi all,
My 84 had some upgraded 7" lights before with slightly oversized bulbs (50/85?) but I decided to go for a newer look and installed my euro headlights. I did all the wiring inside the headlight so I can easily convert back to the US spec lights if desired. I used the same bulbs as the lights that came out, but now I'm having a problem with it grounding. This doesn't make any sense, when my low beams are on they are dim, turn the fog lights on and the fog lights go to candlepower. I would just ground the units but the polarity changes when the high beams kick on. I've used jumpers and a ohmeter to insure I don't have a cold solder anywhere but even with one headlight the ground isn't suffiecient just for the low beam where as before it worked perfectly. Any ideas?

Thanks in advance,
Jeff M.

Did you rewire the internal wiring of the eurospec headlights so that you maintained the four prong US plug?

Yea, actually I just realized it would of been quite a bit simpler to just get the 6 pin plug and swap the order, I forgot how simple mercedes makes their harnesses. :) But yea, it is still using the same four prong plug.

So after giving it some good thought I realized the only thing that could possibly be happening is if the ground is going through wrong by adding resistance. It turns out I had the high beam and ground wires swapped on the H4 harness, everything but the grounding appeared perfectly normal. Thanks for starting to help MTI. :) So happy to have that done, looks great. :cool:

Good thinking. Without seeing a wiring schematic on how you rewired the internals, it would have been hard to help you diagnose. It sounded like the situation where people just plug their old US connector onto the euro headlight pins, which will result in a very dim main beam.