Also check the brushes and comm and the main gears, stiffness in wheelboxes
due to a dry spindle and rack and tube.
or if that doesn't work try
From: Neil Cotty <firstname.lastname@example.org>
To: email@example.com <firstname.lastname@example.org>
Date: 10 August 1999 04:02
Subject: MGA Wipers
>My Wipers hardly work at all. With only one connected say driver side, it
>works, but both together just lock up and freeze unless you give the
>windscreen a whack and that doesn't work all the time which can be VERY
>dangerous considering the weather we've been having here lately. It just
>seems they don't have enough power to move across the screen and they have
>never worked unless the windscreen is wet, which makes it interesting
>getting a pink slip for registration!