92 passenger wiper

The linkage arm( goes on wiper shaft and connects to arm from motor) fell off the splined shaft. I pressed it back on but don't think it will stay. Is there a retainer to hold the arm on spline.
Clark

The wiper arm is made out of soft aluminum and pressed over the splined shaft of the motor. Consequently, when it fell off the shaft, the arm's mount is most likely stripped out and is probably too big for the motor shaft splines to grab hold of.
I've had to repair two Chrysler wiper arms so far as the rear wiper arms commonly strip off when tying to wipe away heavy snow.

Your options are to repair or replace the arm.

To replair, you will need a small bit of masking tape to line the inside of the mounting hole in the wiper arm. One or two layers should do. The thick masking tape will replace the layer of aluminum stripped out of the mounting hole. Mounting the arm (with the retaining nut) should cause the splines to press into the tape so as to hold the arm tight.

To replace the arm, (other than buying one new), you can go to a junk yard and remove one yourself. Be mindful that in removing the arm, you need to take great care to lever it straight off the splined motor shaft without stripping that arm too. These arms weren't made to be repeatably removed.

The arm that came off is on the passenger side wiper shaft not the motor, There does not seem to be any retainer, nut or provisions for one. I guess it is just pressed on the shaft splines
Clark

same thing happened to me with my 97 caravan. I think ill try the masking tape until i get one at a junk yard. Thought about it before, but havent gotten around to it yet. Mine did break when i pulled the wiper up to scrape ice off my winder.