Audi Repair: 99 passat wipers, wiper motor, wipers

Question
when it rains, the either don't work, or move very slowly.  sometimes the car gives
me little shocks when they're not working.  once, i flicked the column stalk to
make it sweep once, it didn't move for about 15 seconds and then moved by itself
(without another flick of the column stalk).  

when i take it in to the mechanic when it's not raining, they work fine, and he
doesn't know what it is.  

Answer
Hi there,

Sounds like a bad connection, most likely one of the connections, remove the sockets on the wiper motor and check for bent pins, corrosion, and lose connections, also check the wiper stalk for the same, if possible swap the wiper motor with another one and see is there is any difference.

also when the problem occurs lift the wipers off the windscreen and try them to make sure the blades aren't causing excessive resistance.