dr bob

I seldom drive the car in the rain on purpose, but K and I had different schedule obligations today and it's been pouring for a few days. So the 928 got to go swimming for a bit. Then the wipers stopped with blades at an interesting angle right across the windscreen. Made it home OK, thanks in part to Rain-X from a couple summers ago. When I stopped in the garage, I could then hear the motor running when I moved the switch. Pulled the plastic cover to expose the motor and linkage. Found that the shaft nut on the end of the wiper transmission was loose. Also found that there's no keying or indexing on the arm where it mates with the shaft; just put it where it needs to be and tighten the nut again. No lockwasher either. Not yet anyway.

Anybody else have a failure like this? The lack of key or indexing looks suspect to me, but crazier things have happened to me before.

Mrmerlin

Dr Bob no key indexing,
run the motor till it parks( with the arm off the motor) then move the blades to the correct position, fit the arm, then tighten the securing nut, the splines on the shaft will lock the arm into position

dr bob

Stan--

I don't seem to have any splines on thetransmission shaft. Loosen the nut up a bunch and the arm moves freely. I may need to take another hard look at the connection and see if there's something missing, like splines in the arm. It's raining tomorrow.

Mrmerlin

There should be splines if not you might try removing the arm and wire brushing the parts as thin metal slivers may have clogged the grooves,
if you have no splines then consider replacing the small arm

blown 87

If they run loose it will take the splines out.
Sometimes you can use a file and a hammer to make it work again.

Tails

drbob.
If you have no splines left you may consider drilling and pinning arm to shaft once it is located in the correct position or use locktite on the taper.
Tails 1990 928S4 Auto