When I replaced the wiper motor on my 1986 240 I wound up with the same problem. Here's what I did:

Pull the glove box and disconnect the motor from the wiper mechanism by removing the link from the motor shaft. Then run the motor a few revs and turn it off. It will stop in the Park position, that's the way its insides are set up.

Moving both wiper arms together as much as possible, place them in the Park position, as close as you can guess.

With both hands in there, work the arm connectors and the little link until the link is close to fitting on the motor shaft. This should not require much movement of the arms at all.

Bolt the link to the motor shaft and try it again. The problem I had was the same as yours. I had connected the link the motor shaft 180 degrees wrong, it seemed logical but didn't work. Easy but embarrassing fix.

Good Luck,

Bob

:>)