Consider installing a volvo washer pump.[8D] These pumps are made by VDO, and OEM for Mercedes (look at your gage cluster, it has VDO stamped on the back). Installed inline, removed check valves at washer jets, one terminal to ground the other hook soldered to the foot switch terminal. Pumps as long as you hold it down and does not interfere with the intermittent wiper timer. Works like a charm. All conections soldered w/heat shrink.