Mark

The symptoms you describe suggest that, at the side where the wiper
arm turns 180 deg with no resistance:

a)    the wiper arm is loose on the wiper shaft (the bit the wiper arm
attaches to)  or
b)    the wiper crank (connecting the relay rod to the wiper shaft) is
loose on wiper shaft, or
c)    the relay rod is not connected to the wiper crank.

To decide which is which, remove the wiper arm and see if the shaft
can be freely rotated, if it can the (b) or (c) are the likely
suspects.  If it can't be freely rotated, reassemble the wiper arm and
ensure that it is firmly attached to the shaft.

If it is (b) or (c), then you'll have to get behind the windscreen to
check the system out.  Bentley says removal of the glove box and
instrument cluster is required to gain access.

Jack Newton

Sydney Australia
'89 Transporter Safari Campervan

PS If it was the motor neither wiper arm would move.

In reply to  Mark Mages who writes:

>The wiper feels like a gear is stripped inside.  When off, I can turn
>the wiper at least 180deg with no resistance, while the one that
>functions doesn't move at all.  If it was just the motor, wouldn't
there