So the 89 740 goes to the local indy for a replacement RPM sensor and an oil and filter change. My daughter is driving it back home, dusk is approaching, and she turns the headlight switch to ON and the headlights come on.

And so do the windshield wipers.

And so it goes. Lights on, wipers on. Lights off, wipers stop. Lights off, wipers operate normally from stalk.

It doesn't do it when the parking lights are engaged, only when the headlights are.

And worse, I just went out to see if the problem existed at both the low and high beam position, and everything is working fine, just like it's supposed to, wipers behaving themselves.

No headlight wipers on the car, if that makes a difference.

Sounds like a short somewhere - any ideas on where to look?