Nokia BH-804 hard reset
To repair and reset your Nokia BH-804 :
Clear settings or reset
To clear all the pairing settings from the headset, switch off the headset, and press and hold the multifunction key (for over 8 seconds) until the red, green, and blue indicator lights start to alternate. After the settings are cleared, the headset enters the pairing mode.
To reset the headset if it stops functioning, even though it is charged, connect the headset to a charger that is plugged into a wall outlet. The reset does not clear the pairing settings.