Opel ASTRA 2017 Owner's Manual page 226

224 Driving and operating
Illustration shows Sports Tourer.
Fitting the coupling ball bar
On Sports Tourer remove cover from
rear bumper by pushing.
Disengage and fold down the
connecting socket. Remove the
sealing plug from the opening for the
coupling ball bar and stow it.
Checking the tensioning of the
coupling ball bar
● Red marking on rotary knob must
point towards green marking on
coupling ball bar.
● The gap between the rotary knob
and the coupling ball bar must be
approx. 6 mm.
● The key must be in position c.
Otherwise, the coupling ball bar must
be tensioned before being inserted:
● Unlock coupling ball bar by
turning key to position c.