To change the contrast on the Suunto Core you need to put it in sleep mode. Note that this erases unlocked logs!
1. Press [START/STOP], [VIEW], [+] and [LIGHT] buttons simultaneously until SUUNTO appears on the display.
2. When the display is blank press [MODE] until the watch wakes and shows SUUNTO.
3. While 'SUUNTO' is displayed, press [START/STOP] until the service menu opens.
4. Press [+] or [LIGHT] to scroll to Contrast and then press [MODE].
5. Change the contrast using the [+] or [LIGHT].
6. Press [VIEW] to exit.