Hello,

There should be a little lever that latches onto the under side of the splined end of the wiper motor post.

You might have to carefully pry that little lever out until you get the wiper arm moving off the splined end.

Most of the time the wiper arm is not or can not be installed far enough onto the splined end, so you might not have to mess with the little lever as it might not be all the under the splined end.

I use a pair of plastic tools designed for removing door panels to pry up on 2 sides of the wiper arm. I also put down a fender cover onto the cowl and hood because sometimes the wiper arm comes off all at once and goes flying onto the cowl or hood.
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Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90501