I'm thinking that car still uses the series circuit between the coolant and windshield washer fluid sensors. For some reason the IC (instrument cluster) figures out the wrong one.

Try disconnecting the washer reservoir sensor and see what happens. (I don't know what should happen so goog luck)

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician