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Discussion Starter #1
My '96 SL320 developed a rather strange electrical problem today and I'm not quite sure where to start. It was a rare dark, rainy/snowy day here in Albuquerque and I had the parking and fog lights on and occassionally the wipers and windshield washer. At one point I noticed the washer fluid warning light come on but didn't pay much attention to it. When I stopped and turned off the CD player I could hear a nasty clicking/humming sound from the engine compartment that stopped when the light switch was turned off/started when I turned it back on. The fluid reservoir was dry. After refilling the reservoir I discovered that the headlight washer pump runs constantly as long as the light switch is in any "on" position. The headlamp wipers do not run (unless the main wiper are on). I pulled fuse #1 which has temporarily cured the problem. Any suggestions??
 

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My '96 SL320 developed a rather strange electrical problem today and I'm not quite sure where to start. It was a rare dark, rainy/snowy day here in Albuquerque and I had the parking and fog lights on and occassionally the wipers and windshield washer. At one point I noticed the washer fluid warning light come on but didn't pay much attention to it. When I stopped and turned off the CD player I could hear a nasty clicking/humming sound from the engine compartment that stopped when the light switch was turned off/started when I turned it back on. The fluid reservoir was dry. After refilling the reservoir I discovered that the headlight washer pump runs constantly as long as the light switch is in any "on" position. The headlamp wipers do not run (unless the main wiper are on). I pulled fuse #1 which has temporarily cured the problem. Any suggestions??
Chances are your problem lies where the wipers end up. If they end up below the bottom tit on the headlight, they will try to pump as long as the lights are on.

To fix the problem, flick the wipers back so that you can see the nut. With the wipers off of the headlight put the headlight on and press the washer button.
Then loosen the nut, pull out the wiper and reposition it to just lay on the bottom tit. It should end up being parallel to the bumper.
 

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mhabie....thanks for the reply. I just gave that a try, but no matter what I do, the instant I turn on the light switch the washers start spraying (forcefully!).
 

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Headlamp washers? Most of us have given up on those long ago. Our German Engineering Friends were just bored when they came up with those. Tuck them under the litte tit and forget them. :cool:

Watch my next post.
 

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mhabie....thanks for the reply. I just gave that a try, but no matter what I do, the instant I turn on the light switch the washers start spraying (forcefully!).
Does the spray come on to the windshield also? Or, just the headlights. Could there be a chance that the push switch on the column is stuck?

You can always disconnect the wiring to the headlight pumps.
 

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Plink49, you need to replace the right headlight wiper motor assembly. It has a relay built into it to cycle off the headlight washer pump. It was a very common item to be replaced on the 129's. When I purchased my SL500 the headlight pump was unplugged, indicative of a bad right side motor. And sure as shi%, when I plugged it in it ran continuously and emptied the resovoir in about a minute. alloemautoparts.com have it for $121.34, and Autohaus Arizona lists Bosch for $118.14 as a special order item. I think I bought mine from alloemautoparts.com. Its a pretty easy task to replace. Hope this helps. Keep it original..............Thor
 

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msmith66....I found that recall. It's NHTSA #96V175000 and it affects 28874 vehicles from 1990 thru 1996 including all SLs except 600s as well as other models. Anyone know how long MBUSA honors these recalls? Can this still be corrected at no cost?

Thorgod....after finding a wiring diagram for the headlamp washer wiper circuits, I narrowed the likely culprit down to either the Right Hand Wiper Motor which you mentioned, or the HCS Relay Module. I don't know what HCS stands for or where the relay is, but the positive voltage for the washer pump comes from the Wiper Motor, so that is most likely the part I need. But I think I'll just unplug the pump wire and replace the fuse. That way the wipers themselves should still work, and I'll save $150 for something I don't really need or want.
 

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I heard that MB will try to get out of the recall fix on models that are out of warranty but I've also heard that they do a lot of goodwill fixes. If you are a customer or they think you will come back to be a customer, they would certainly consider fixing it. I'm not so sure that they can decline to fix a safety issue though. If you call one dealer and they poo-poo you, don't hesitate to call another.

Good work on finding the recall. Most later model R129s were fitted with xenon lights, which in the U.S. don't have wipers so its not much of a problem.
 
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