'91 500sl washer fluid pump stays on
 

windshield washer fluid pump got stuck and would not turn off. only happened with lights on. when i turned lights off, pump turned off. also seems to be more with headlamp washer than windshield. fluid poured out nonstop on headlamps, but only when i pushed in switch for windshield. been having the typical signal light/cluster problems as well, which i have read a lot about on this forum. not sure if related.

Check your owners manual.... The wipers on the headlamps only come on when the headlamps are powered AND the windshield wiper is activated. It's a known issue that the motors in the headlamp wiper fails and the blade stops in some position other than the end stop. So, the parked position is not sensed and the pump will continue to run. In fact, it will empty all the fluid and then often burn itself up. Disconnnect the power to the pump until you repair or replace the motors on the headlamp wipers. Use the search function of the forum for much more info.

And until you fix it, pull the lead from the headlight pump so you don't start a fire.