David,
Congrats. on your "new" 911! I saw a bunch of pics of it over on Rennlist...very nice.
I have the same washer sys. in my SC, switch under the dash lip near the clock. I have never used it & honestly do not even know if it works. I think it has something to do w/. the headlight washers??
My first Porsche was my 82 SC, it had about double your miles when I bought it.
I remember the feeling, that never goes away