Headlight washers stopped working (W210)

[aTOMic]

I bought the car ('96 E320) about a month ago and they DID work once, spraying copious amounts on the lights, the hood and into the open windows of the cars on either side of me (I'll not try them while stopped at a red light again ) but now they don't work. I have tried to listen for a sound of the pump, but it sounds like the pump is not running. I would not suspect the switch is worn out, since it gets so little use; I have pushed it a thousand times to try to wear off any oxidation that could be preventing the circuit from being completed, I have checked the fuses, and there is plenty of fluid in the reservoir. Has anyone fixed this problem in their car and if so, what was the cause? Also, where is the pump?
TIA, -Tom