Garmin 255A manual Set to a low level, Mixed with Com, Check Mic key input, It can be enabled

Problem

Possible Cause

Action

GNC 255 does not power on	No power to the	Check power connections,
	GNC 255	breakers, and main
		avionics switch
	Faulty electrical	Contact your dealer to
	wiring or connection	perform electrical system
		test
No Nav audio	Output disabled or	Contact dealer
	set to a low level
Nav audio in Com	Mixed with Com	Contact dealer
	feature
GNC 255 does not transmit	No power to Com	Check power connections
	Mic key connection	Check Mic key input
		connection
Intercom doesn’t function	It can be enabled	Check connections
	or disabled via a
	remote mounted
	switch or via the
	menu.
	No voice activation,	Check ICS page, Intercom
	or if must talk too	On/Off, Adjust Intercom
	loud
Can’t change active frequency	Com Radio not	If in Lock Out mode,
	communicating. The	press the external Com
	radio may also be in	FLIP/FLOP key for two
	lockout mode. In this	seconds to return to
	case the radio would	normal operation or cycle
	be tuned to 121.50	the avionics power. If the
	and the active freq	condition persists, contact
	would not be able to	dealer.
	be changed.
OBS readout displays “---”	Resolver failure	Contact dealer
	Calibration error	Recalibrate resolver

4-2 Garmin GNC 255A/255B Pilot’s Guide 190-01182-01 Rev. A