intermitent wiper control unit

[winecountryone]

My intermittent wipers worked up until 2 days ago.They quit "mid sweep" while running.I tried to trace the wiring but it disappeared into the harness.The other 2 speeds work fine.
FWIW the washers aren't working either.This is a 74 450SL.
I'm assuming the timer box quit working after 36 years.Where is it located and would a replacement have to come from a 107?
I thought the EPC might be of help but I am unable to access it.All 3 of us in the house use various flavors of Apple running OSX 10.4 which is NOT SUPPORTED by Mercedes Benz at this time.