Headlights turn my intermittent wipers on!
 

I have a strange electrical problem on a "87 190E that I hope someone can help me with. Whenever I turn the headlights on the intermittent wiper starts. I have replaced the intermittent wiper relay. Upon further investigation I have found that removing the fuse for the right side lights prevents the intermittent wiper from starting. Any clues?

quick question, does it just swipe ONCE and then stop? if so, my 126 did it for a while anytime anything power was operated(sunroof, headrest, rear defroster, a/c turned on). Alternator and battery came up fine after repeated tests, and no faults/shorts founda anywhere. I accepted it as a fluke thing that gave the car "character" and once i accepted it it just stopped. Go figure
Ryan

No, it keeps running on intermittent, and though it does rain a lot here, it does dry out every once in awhile.

I've seen strange behaviors similar to this caused by corroded ground points in the electrical system. To troubleshoot it you really need to have the official MB Electrical Troubleshooting Manual. Research the right headlight & wiper systems - see if they share a common ground.

On my 124 chassis car, each headlight is grounded to the chassis immediately below the headlight assembly. Look for a bunch of brown wires coming together and bolted to the frame of the car. Your 201 may be similar, seeing as these cars are cousins design-wise.

Thanks! I'll check that out this afternoon.

All the grounds at the headlights were intact. Got a tip from another source that it may be related to the headlight washer mechanism, so I will be checking it out tonight.

Just because they're intact doesn't mean they're working. A thin layer of corrosion between the electrical fitting and the body of the car is all that 's require to muck things up.

It's a bit inconvenient to clean up these grounds - the headlight assembly has to be removed. Here's a quick way to look for the problem. Go get a spray can of electrical contact cleaner - I buy mine at Home Depot. Give one of these grounds a good shot of cleaner. Then go turn on the headlights - see if the wiper goes. If you find a ground which stops the wiper - that's your problem. Spraying the ground is a temporary fix - it'll last a day or two - so you'll have to go in and clean it up the hard way.

BTW, the ground for the headlight washer system is the same place I sent you looking. I know from experience that if the headlight washers lose their ground, the windshield wiper will refuse to shut off - though in my case it was on low speed, not intermittent.

Okay, I took your advice to heart. Removed both headlight assemblies, re-soldered all three ground terminal wire assemblies and wire brushed the body connection area at the ground screws. Still getting the same problem.

Have also noticed that turning the headlight switch one notch counterclockwise to the right side valet parking position will cause the wipers to start when the ignition key is in the accessory position but not in the run position. Turning the headlight switch clockwise to the parking or headlight position will cause the wipers to start if the key is in either the accessory or run positions.

Have ordered a factory electric troubleshooting manual.

Darn! Well, I'm now out of ideas.