Yes - the optical horn is when you flash your headlights. That's what MB calls it in their fuse panel. I was playing around and flashing the 100Ws and then uh-oh, what's that smell??? Anyway it was not really a big deal. This was in my 79 123 and everything was already a little marginal.

IMO I think the Euro housing, switch and wiring can take the wattage. I used it for about 3-4 months (normal use with no exessive flashing!) with no side effects, only uncertainties because of my marginal alternator. If you are uncertain, there's a lighting harness you can make up or buy with relays. If you really like using them then I wouldn't worry about it. But I didn't really need the extra lighting....

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1992 124 E200 (Euro)