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Old 08-30-2022, 05:18 PM   #2
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sledge's Avatar
City: Jacksonville
Vessel Model: American Tug 41
Join Date: Sep 2018
Posts: 230
I have a GMR 18HD. There are two cables going up to the 18HD; one is the RJ45, the other is the two DC power wires in a connector.
Typically radar and chartplotters have power lines running to a common DC power bar, so when a breaker called "electronics" or similar is flipped, it turns on the whole helm.
If that radar has lost connectivity, even just due to the RJ45, it will not show up on a Garmin menu. If you un-bolt the radar enough to get under it, you can manually unscrew the two connectors and check them; I've had mud dobbers/bees try to build a nest under there and disrupt the RJ45. It might just need to be cleaned out and reconnected.
Once disconnected, you could also flip on the breaker and put a multimeter on the power cable to check if it is receiving 12VDC. However if you do this, be sure to turn the breaker off again before you reconnect to the radar, you don't want it trying to power up when you're up there working on it.
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