Yes, it was a surprise
 

Recently I purchase a sweet looking W124 - 1995 E420, with 147,000 miles.

A real head turner.

But it came with some haunts. One was the windshield wiper. It would always be on in the intermittent mode. Well I bought the car thinking it was a bad switch. The switch could wait, so I replaced the engine wiring harness.

Yep, the car ran better after the harness, but the windshield wiper stopped it's haunt. Yes, after replacing the wiring harness, the windshield wipers started working normally. On when I switch on, and off when I switch off.

I would not have guessed the Engine wiring harness would impact the wipers.

Well, engineered like no other car in the world.

That story ended happy.

But if you can help explain how one is connected to the other, I would appreciate it.

it would have been a wild ground. if the harness was broken, turning a ground into a positive, then strange things can happen. Like causing normal and fast speed to have two positives instead of grounds. Stranger things have happened