W123 Windoe Wiper Issue

_____ Hello All,
Subject car is 1985 W123 300D turbo diesel. Problem is window wiper suddenly stopped working on a) intermittent,
b) low speed. Now it only works on high speed, and does not park in the usual wiper blade position.
I searched the iNet and this group, but found little of significance. Schematic in Haynes Repair Manual is too small to read.
Solution tried so far is to replace motor with known good one. This did not solve the problem. Could the interval timer relay be responsible for the observed behaviour?
Does anyone have a large schematic to help with diagnosis of the problem?
I know where to find the relay behind the instrument cluster. Can someone confirm what the colour and size is, plus the Mercedes part number?
If you have schematics, please send to "con_trx at shaw dot ca".
Thanks in advance.
/ John

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