The heater for the washer fluid in all of my cars is part of the engie cooling system. In my E's, 190, and SL, a radiator line goes into that washer bottle, through some metal piping, and then back into the system. Perhaps those wires are part of some sensor.

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-Justin

91 560 SEC AMG - other dogs dd
01 Honda S2000 - dogs dd
07 MB ML320 CDI - dd
16 Lexus IS250 - wifes dd

it's automatic.