It sounds like a hardware
problem but a few easy checks:
1. Is your software
up to date? You can check the software
version number under the "communications" part of the 4210. Current
chartplotter version is 6.10 and radar 3.1. Both matter. It's easy to update software on a Garmin if you you have an SD memory card reader on a computer and an SD card - like from a camera
. The readers are cheap
to buy these days too. You download the update free from the Garmin support web site to your computer and then copy it to the SD card (Garmin provides a program with the download to do this). Then stick the card into your 4210. It takes it from there - updating everything on the network.
2. Try unplugging everything but the radar from the 4210 (eg. NMEA 2000
and NMEA 0183
cables and any 2nd chartplotter ). There's an outside chance that another device is messing up the radar or causing network problems. Not likely, but easy to check.
3. Did you cut and splice the network cable during installation
at the mast
? If so, go back and check that splice. Try seperating the wires at the splice a little more. These are Ethernet cables and they don't take splicing very happily.