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

Page 54
Image 54
Garmin 255A Set to a low level, Mixed with Com, Check Mic key input, It can be enabled, Or disabled via a Remote mounted