Just finished going through this mess on one of my projects. Went and bought the electric wipers. Because, after wasting many efforts trying to fix the vacuum wipers with automatic tranny fluid, checking and re-checking hoses and fitting nothing worked. I started the install of the electrics and in dismantling the vac connection at the manifold discovered a brass fitting was loose, only less than a 1/2 turn with the wrench. So, I thought, what the hay I'll give it a goose to see what happens. Gave the old, a test and like magic, the old boogers worked like a charm. I obviously had neglected to closely check just that one fitting. Sooooo, it was then decision time. Do I stay with the old or go with the new. After a cup of joe and chat with the real boss, decided to go with the new. Works for me, may be different for others. Lesson learned check, recheck and then check again.
