W124 washer bottle heating

[wally]

Hi, I've noticed that the washer bottle is always really hot, even on a hot day. It seems there is an electric control valve/servo for it, on the passenger side next to the firewall, presumably this valve is always open. The line coming off of this valve also seems to go to the heater valve on the inside side of the firewall.

I'm concerned because I've already broke one of my washer pumps (for the headlights), I'm thinking now that because the bottle was always hot it caused the plastics to get brittle over time and crack.

I haven't been able (yet) to locate any information on these parts yet and what determines when this valve is open or closed. Does anyone know how this part of the heating system is supposed to work?

'91 300E 205000 mi.
Purchased, 9/2002, 178000mi. DIY repairs: brakes (caliper ceased), water pump (leaking), EHA (leaking), brakes (pads gone), mufflers (broke off), radio (draining battery), warning buzzer (fried circuit), steering linkage (ball joints gone).