Thanks to Dave Turnblom, a former SHOwner:

I tried a tip found in rec.autos.tech and thought it worth sharing. My SHO had a problem with the intermittent wiper setting forgetting to continue wiping (had to twist a bit) and Mama's wagon wouldn't pump washer fluid without jiggling the switch (thought it was pump for awhile). This tip fixed the wagon, I wish I knew it when I had the SHO.

Pop off short end cap from wiper stalk. It is only the tip of the part you rotate for wipers. I pried from the dash side in case I marred it. A screw is now visible. Take it out and (with a rag to in place to catch pieces) remove the knob.

The detent mechanism is simply a spring across and through the stalk with end caps. The intermittant wiper variable resitor type contact pad is in the base end of the stalk. A piece under the knob has contacts that hit different point of the contact pad as you rotate the knob. Washer contacts are in the end of the knob.

Clean out the existing grease. Mine was rather thick which I think was the problem. The rec.autos guy thought it was dirty contacts. I cleaned all with solvent. With the contacts propped up with a Q-tip I also cleaned them with a pencil eraser. The Q-tip was also used to slightly bend the contacts to increase contact force. Before assy I put a light coating of dielectric grease on parts.

The wiper stalk (multi-function switch in Ford parlance) is expensive. The faults are irritating. The cure is simple and free. Enjoy.