Q. What do the flashing LED lights on my NGT-1 mean?

NGT-1-MTC Trouble shooting guide for LED flash

These are the expected NGT-1 LED flashing sequences for a ‘working’ installation, and various other possibilities.

NGT-1 LED sequence on NMEA 2000 power-up when MTC is already connected and active.

1. First both ends of the NGT-1 will alternate rapidly for about one second.
2. Then, the NGT-1 will remain dark for a short period. If the rapid flash sequence does not stop, see NGT-1 LED diagnostics.
3. Then the NGT-1 NMEA end will start flashing slowly, at a one second rate.
4. After the NGT-1 NMEA end has flashed once or twice, the MTC end of the NGT-1 will flash twice. (This indicates that the MTC has recognized that NMEA 2000 is back online, and has reinitialized NMEA 2000 functions.) These two flashes may be in unison with the NMEA end flashes, or may alternate with respect to the NMEA end flashes.
5. Once the  MTC has reinitialized NMEA 2000 functions, the steady state is for the NMEA end of the NGT-1 to continue to flash slowly.

NGT-1 LED sequence on NMEA 2000 power-up when the MTC is not connected.

1. First both ends of the NGT-1 will alternate rapidly for about one second.
2. Then, the NGT-1 will remain dark for a short period. If the rapid flash sequence does not stop, see NGT-1 LED diagnostics.
3. Then the NGT-1 NMEA end will start flashing slowly, at a one second rate. This will continue unless and until an MTC is connected.

NGT-1 LED sequence on remote reset of the MTC.

1. Since the NGT-1 and MTC are already operating, the NGT-1 will be flashing slowly prior to sending the reset to the MTC.
2. After the reset command is sent via the mobile app, it may be several seconds before the MTC actually starts its reset sequence.
3. The reset sequence start will be indicated by the Orange LED on the MTC blinking once, followed by several blinks from the Green LED.
4. After several seconds of independent/alternating blinking of the Orange and Green LEDs, both LEDs will blink together followed by two blinks at the MTC end of the NGT-1.
5. After a few seconds of blinking together, the Orange and Green LED will go on solid, at which time the MTC end of the NGT-1 will blink twice.
6. The steady state following reset and reinitialization is for the NMEA end of the NGT-1 to continue to flash slowly, at a one second rate.

NGT-1 LED sequence on NMEA 2000 power-up when MTC is already connected, but there are no NMEA 2000 devices or there is a termination problem

1. First both ends of the NGT-1 will alternate rapidly for about one second.
2. Then, the NGT-1 will remain dark for three to four seconds. If the rapid flash sequence does not stop, see NGT-1 LED diagnostics.
3. The MTC end of the NGT-1 will flash twice.
4. Then both the NMEA end and the MTC end of the NGT-1 will begin to flash in unison every four seconds. This will continue until other NMEA 2000 devices come online, or the NMEA 2000 terminators are added to the backbone.