Volvo 2008 S40 Owner's Manual page 66

The earth is divided into 15 magnetic zones. The compass is initially set for the zone to which the car was delivered,
and should always be adjusted if the car is driven to a new magnetic zone. A "C" will be displayed if calibration
becomes necessary.
To calibrate the compass:
1. Stop the car in a large, open area, away from traffic.
2. Using a pen or similar object, hold the button (1) depressed for at least 6 seconds. "C" will be displayed.
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02 Instruments and controls
Mirrors
3. Press button (1) for at least 3 seconds to display the number of the current magnetic zone.
4. Press button (1) repeatedly until the number for the required geographical area (1-15) is displayed. "C" will be
displayed again.
5. Drive slowly in a circle at a maximum speed of 6 m.p.h. (10 km/h) until a compass direction is displayed.
Calibration is complete.
Power door mirrors