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Old 02 April 2009, 12:26   #1
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Lowrance problem - report, not request

Took a couple of days off, and decided to spend 4 days diving in Monterey (Calif, USA.) Weather didn't exactly cooperate, but that's another story.

What did happen was that, on Saturday, just before leaving the dock, my GPS (Lowrance LMS-520C) suddenly decided to give me a "Position Lost" error message, followed by a "GPS Module not Responding" message.

A bit of background here: The Lowrance unit uses an antenna that connects to the GPS via a "plug and bayonet" connector (I.e. you align the key, push the connector on, then twist the collar on to lock it in place.) As simple as that sounds, the antenna is part of the NMEA 2000 network, so you also have to connect the network power wires to a 12V power source. Any other sensors you may have (I have a fuel management sender; you can also get fuel tank level, radar, and a bunch of others) get connected into the network as well, basically daisy-chained into the antenna cable.

So, given the failure mode, I figured one of two things had happened: Either the antenna had bit the dust, or the network wiring had gone away. Since there was no way to troubleshoot the antenna in situ, I concentrated on the wiring.

The wires for the network power come out of a similar connector (if not the same connector; don't remember) as the antenna; but are simply exposed wires that the installer is supposed to terminate to 12V. For some dumb-ass reason, Lowrance has decided to use something like 24 or 26 ga stranded wire for these connections. This causes a couple of potential problems: If you use crimp connectors (as the ABYC recommends), the small diameter of the wire make for a tenuous connection, as the crimps don't reliably grab the conductor. If you decide to solder the connection, the small conductor diameter and solder makes for a connection that is very stress-prone.

Almost immediately, I found a wire that had succumbed to both problems. Despite being in an area that was not subject to much movement, the wire had broken at the spade connector. Attempts at opening the connector and recrimping were only partially successful; only when I soldered the wire onto the connector did the problem fully resolve itself.

I don't see why the wires for network power should be so small. I understand there is very little current going through them, but handling and durability suffers with this size wire, and the loss of a connection brings down the entire NMEA network. Not a great design, IMO.

Anyway, that was just a heads up for other Lowrance owners. Hope you don't have to solve similar problems.

jky
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Old 02 April 2009, 16:46   #2
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I know what you mean. Most signal wires on GPS units are pathetically small, as are some power wires.

However, you can connect power to a NMEA backbone at any point you like. The best solution would be to bin the Lowrance connection and get another T piece and a power drop cable. The new power drop cable will be designed for 4 amp supply (standard NMEA 2000 capacity) so be much beefier.

In addition to this the Lowrance GPS head unit needs it's own power supply connection which you can't do much about though.
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Old 02 April 2009, 19:08   #3
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Understood, but once the network leaves the console, there is no 12V source to connect to.

I think, if I ever have to redo things, I'll put some kind of block in to transition from the small gauge stuff to a larger gauge that does the run to the supply voltage.

Thanks for the reply;

jky
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Old 03 April 2009, 03:38   #4
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I would be interesed to know if it is the older 'blue' network or the newer 'red' series??

I had a load of issues with the blue system and it was completely replaced by Lowrance with the new red cables.

As an aside, Raymarine use power cables that are almost the size of jump cables!
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Old 03 April 2009, 11:26   #5
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520C uses the red network. As I recall, the wires on the blue were the same (though I am not positive about that.)

The wires in question come out of the larger connector (rather than the small network connector); as supplied, they're about 2 or 3 feet long, and the ends are simply stripped back. Little tiny guys.

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Old 03 April 2009, 12:48   #6
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We had similar issues to JABS and it was fixed same way. Interesting that the LGC2000 has been quietly retired leaving I think only the LGC4000 left, also the new HDS range all have in ternal antennas.

I'd love to know a bit more about how easy the new HDS software is to drive.
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