Alex even though I spent many hours over the last several weeks under the dash of my 51 dinking with the wipers, I can't say for sure if the drive arm hexs rotate. But I'm about 89% sure they should.

My experience after much effort to both rehab two vacuum motors and adapt a 6volt VW electric motor...I finally broke down and sent the best of the two vacuum motors to Wiperman (at Wiperman.com) and a week or so later had a rebuilt motor (with a 3 year warranty) that works like a champ. Zero complaints here.

Good Luck
Ron


RonR


1951 3600 with Clark flatbed, T5, 4.10 rear
1970 340 Duster
1990 5.0 V8 Miata (1990 Mustang Gt Drivetrain)
1964 CJ5