Spastic S500 windshield wipers
 

OK, here's a potentially ugly gremlin. I searched and didn't come up with anything, so maybe you can give me some tips.

My father's 2000 S500 has windshield wipers that are on crack. It's fine at first-start of the day, in a comparatively cool garage. But when the car is out and about and heats up (100+ degree, humid days down here right now), the windshield wipers randomly and unexpectedly come on with no switch input. They just start! If he cycles the switch on and then off, they turn off and park properly. It only seems to happen when the car is hot, having been parked on a lot in the sun or something.

No dash lights showing. We're not in the same town at the moment, so I can't plug in my code reader. Any tips/thoughts? Thanks!

Cheers, John

Most likely a computer is causing the problem.
ON that car & most MB's after 1998 there are a network of computers to operate all body functions.

You need to have codes read from that interior network.

Maybe something to do with the rain sensing function?

Possibility, IF they are selecting that position with the switch.
But sound like that was the case?

Thanks for the info about the computers -- I had read somewhere that a lot of electronics were involved in this car.

The switch is definitely in the OFF position when the wipers randomly come on. Dad has owned the car since new, so it's not an operator error (insert I/O joke here). It might have something to do with the intense heat lately -- over 100 degrees the last few days where they are.

I'll tell him to swing through the dealership and have the computers scanned. I always shiver at the thought of chasing electronic gremlins and the associated cost, especially when so many dealers choose to just throw parts at a problem rather than actually diagnose. There are exceptions, I know...

I'll post back if/when we learn anything.

Cheers, John

Incidentally, a funny coincidence... Dad discovered yesterday that if he turns the wipers on to the intermittent/rain-sensing mode, they do NOT come on randomly. (The weather has been dry.) Odd. This might be the stop-gap solution until he gets a dealership to scan it, or depending on the repair cost, might be a permanent solution. I'm trying to bully him into a new sports sedan, but he's sure attached to that S-class.

Cheers, John