Simrad AP28 Operator's Manual page 76

Clutch:
This is the default setting and it allows you to steer the
boat with the helm or wheel when in STBY mode. The
port will activate (go high) in all active steering modes,
and typically engage a bypass valve on a hydraulic linear
drive or a clutch on a mechanical drive.
Auto:
This setting is implemented for future use. Always use
the "Clutch" (default) setting.
Rudder Test
The Autopilot Computer will after a few seconds issue a
series of PORT and STBD rudder commands and
automatically verify correct rudder direction. It detects
minimum power to drive the rudder and reduces the
rudder speed if it exceeds the maximum preferred speed
(8°/sec.) for autopilot operation.
The Rudder test is verified by the display showing
'Motor OK', or 'Failed'. If 'Failed' is given, check for
correct electrical connection.
Also refer to "Alarms" beginning on page 111.
76 | Setup at installation
If the boat uses power assisted steering, it is important
that the engine or electric motor used to enable the
power assist steering be turned on prior to this test.
Stand CLEAR of the wheel and do not attempt to
take manual control of the wheel during this test!
Bring the rudder
manually to midship
position before
starting the test.