The wipers on my HJ have always seemed a bit sluggish. Not surprising really, 4 decade old motor. But I had the plenum cover off recently and noticed that the sheet of metal where the passenger side wiper is mounted had been pushed down a bit. Also the mounting holes were a bit recessed downwards in the metal as well.
No doubt this is due to me and previous owners thumping them on with their hand. Oops.
A quick bit of tapping/levering/persuasion brought the metal back up to a flatter, normal looking level.
I refitted the arm and gave the wipers a go. Abracadabra! Much better. They were moving much more freely.

So if you are having a bit of trouble getting the wipers to work well it might be worth having a look at the mounting plates. In HJs, on the passenger side it is a bit of sheet metal with downturned edges. Easily pushed down. I reckon this was causing the arm to rest on the plenum cover when it was right down so giving a lot of resistance. Hope that helps.

Edited by user Sunday, 30 June 2019 6:04:45 PM(UTC)  | Reason: Not specified