Simrad AP28 Operator's Manual page 83

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.
Proceed as per display
instructions and immediately
release the key when the
rudder reaches the port hard
over position. The rudder will
now be automatically centered.
Setup at installation | 83