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Old 02-01-2009, 12:43 PM
techguy512 techguy512 is offline
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Join Date: Apr 2005
Location: Austin, TX
Posts: 631
More info and Clarification

Guys, I just want to clarify some things here. Mercedes made some considerable modifications to the pulse wiper systems since they were first introduced in the mid 1970s. There has been a "progression" of different pulse wiper control relays during the history of the system, and this little upgrade module I've made has been tested to work with SOME of them.

The first incarnation of the relay is part number 123 821 00 63. It is shown in the first photo labeled "Old Style" below. The only manufacturer I've found is Bosch, and my module works with it. It was used in the older W123, newer W114, W115, and W116, and W107s between about 1975 and 1980. It's housed in a metal can and it's a ***** to work with, but it does work.

In about 1981 there was a simplification done to the relay, resulting in part number 000 821 08 63 (you can sometimes find parts labeled 000 821 07 63). This is shown in the second picture and is a plastic housed part. There are multiple manufacturers like Bosch, Siemens, LK and others. It was used in later W123s, later W107s and W126 through 1985.

Big changes happened in 1986, when the relay changed to a "multifunction" relay similar to that used in the W201. Based on my reading of the limited documentation I have, this new multifunction relay controls not only the interval wipers, but the rear defroster as well as some level of emergency flasher function. The control is to some extent digital, in that the relays I have taken apart use a single IC to control all of the function.

I had intended to do the work necessary to integrate my upgrade module into the multifunction relay, but in order to do this I need some documentation above and beyond that which I already have, such as car wiring diagrams, etc. Early last summer I had enlisted the help of this forum's (and likely the world's) foremost expert on the SDL, but I DROPPED THE BALL and failed to follow up. In order to make this a reality for the multifuction relay, I need to trace wiring diagrams to decode functions, reverse engineer circuit board layouts to figure out how to integrate my circuit into the existing frameworks, and build test fixtures to ensure my upgrade hasn't degraded any of the non-related function. The amount of work needed is substantial.

Anyway, at this moment if your car uses a relay with a part number of xxx 821 yy 63, where xxx is either 000 or 123 and yy is 00, 07, or 08 then this work is already done. This should cover almost every car made by Mercedes between 1976 and 1985 - with the glaring exception of the W201.
Attached Thumbnails
Anyone ever add a momentary switch for the wipers?-old-relay.jpg   Anyone ever add a momentary switch for the wipers?-new-relay.jpg  
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