I know nothing of the car's history...I just purchased it, but I'd bet that this isn't due to a modification. I talked to the previous owner, and he said his mechanic said it was the "wiper module"(???....eh?).

I can tell you what it "isn't" from switching "known good" parts from another W124 I have here for sale and a little more research. It isn't the "mutifunction relay" or the headlight washer relay, or the wipe/wash switch. Also....I was mistaken on the headlight wipers....they don't arbitrarily park straight up....they park wherever they are when you release the washer switch (with the headlights on).

Completely baffled...

Jim