MG ZR Series Owner's Manual page 80

Wipers & Washers
Rear window wash/wipe
Rotate the switch clockwise to the first position to operate the rear
wiper. After wiping continuously four times, the wiper continues
intermittently until switched off.
Rotate the switch further clockwise, to the second position, to
operate the rear screen washer AND wiper. Hold in this position
for the required duration of the wash.
Rotate the switch anti-clockwise to operate the rear screen washer
and wiper. The wiper will operate for the duration of the wash and
continue wiping a further three or four times once the switch is
released.
NOTE: If reverse gear is selected while the front wipers are operating (at
any speed setting), the rear screen wiper will operate automatically for three
wipes.
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