Emphasize "BACK" of the fusebox. The brass connection bars are exposed to air and moisture, and are riveted together. The brass corrodes and the connections get worse and worse. The original bulkhead insulation put in many Minis is great for holding moisture in there.

Cup Cake gets the prize.  Minicop came over yesterday and we checked the 5/6 fuse with a VOM.  It was bad (but looked good).  Replaced it and his wipers, tach and heater blower are all back up and running.  We also removed each of the fuses in the block and (attempted to) clean the contacts for good measure.

check the back of the fuse box for corrosion also.

Interesting. On the 88 plus wiring diagram there is a direct connection between the wiper motor the the tach by way of the light green/orange wire. The wire goes directly to the wiper/washer switch with a take-off to the wiper motor and then take-off to the tach. This wire originates at the 5/6 fuse and also appears to power up the windscreen washer pump. If the washer pump insn't working as well this would appear to be your problem. I would check the fuse. The wiring diagram shows the fuse is at the end of the bloc but it could be somewhere else in real life. The input wire to the fuse in question is light green/white. Otherwise you need to check at the first connector  after the fuse block.

How about removing the electrical plug from your windshiled wiper motor and check for voltage? Is there any when wiper switch is operated? Are all your fuses in tact, have continuity? 

It's a 93 SPI. I really need to get a Haynes manual.

Does your wiring diagram show a common circuit between the tach and wipers? I could look in my Haynes which goes uo to 91, if any use to you, but you need to specify the year.

So I'm trying to figure out what is going on with my RPM gauge and windshield wipers. Neither of them work. Any ideas?