Melted my SeaTalk NG connector

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Hal Mueller

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Jun 18, 2022, 12:11:18 AM6/18/22
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I’m looking for a sanity check on what I think is the cause of the problem.

I’m replacing my nav panel, including a new breaker panel. All of my nav electronics are Raymarine/SeaTalk NG. One change I made was to split out the power to the SeaTalk bus to a separate circuit from the one for the autopilot. I now have 3 breakers, each one 15 amp, for the Raymarine electronics: Seatalk bus, Axiom chart plotter, autopilot (AIS and Fusion stereo, which are also on the Seatalk bus via adaptors, each get their own breakers too).

I powered everything up yesterday from the new panel, and everything worked fine. Then I experimented with turning some things off, including the autopilot. I sat down, letting things run, and dozed off. I awoke to a pop as a breaker tripped, and saw a small puff of smoke in the galley. Uh oh. The breaker for the SeaTalk bus had tripped. Reset, turn it on again, and it’s drawing heavily, with a voltage drop from 12.7 to 11.6. It trips again in about 45 seconds.

I finally thought (today) to look at the autopilot ACU. Here’s what I saw:

image0.jpeg
image1.jpeg

jkr...@aol.com

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Jun 18, 2022, 8:28:45 AM6/18/22
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I went through a rehire recently and just this winter replaced the autopilot. I don’t remember exactly, but I don’t believe there should be any interconnect of the power between the acu and the sea talk buss. I would review the wiring at this juncture carefully. Also there is a fuse in the acu . Is that still good? It should have blown before your smoke occurred.
Ron
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The charred white connector is on the cable that goes from the backbone to the autopilot ACU.

My working hypothesis is that, with the autopilot powered off and the Seatalk bus powered on, I was trying to power the autopilot through the Seatalk bus, which is supposed to be fused at 3 amps (instead of the 15 amp breaker).

My plan is to replace the 15 amp Seatalk breaker with a 5 amp one (the smallest available from Blue Sea in that form factor), and to NOT connect the red power wire on the replacement riser cable. There will never be a time I want to power the Seatalk bus from the autopilot; it will always have its own dedicated circuit.

Is there any bad thing that might happen if I don’t connect the Seatalk power to the ACU? The ACU has its own dedicated 10 ga power supply.

Hal Mueller
halmu...@gmail.com
S/V Yard Work, Beneteau 323

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Hal Mueller

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Jun 18, 2022, 9:58:34 PM6/18/22
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Thanks, that’s helpful!

Manuals show two fuses on the ACU, one for the ACU itself and one for SeaTalk NG. They also show a power switch at the SeaTalk NG connection. My ACU-100 has neither. There’s a 10 amp blade fuse, plus a 10 amp spare in the lid. This makes sense to me, because the manuals explicitly state that an ACU-100 can’t supply power to SeaTalk NG. 

I have to replace the riser-to-lugs cable (which melted), and when I do, I’ll air-gap the red power connector. 

For folks who don’t normally mess with RayMarine gear: the 5 way connection in the bottom of the photo below is the SeaTalk NG. The 4 way is the rudder sensor, deliberately miswired (green/red) because the original installer miswired the sensor connection. Heavy red/yellow is the power to the ACU. 

image0.png

Hal Mueller 
S/V Yard Work

On Jun 18, 2022, at 5:28 AM, 'jkr...@aol.com' via Beneteau Owners <benetea...@googlegroups.com> wrote:

 I went through a rehire recently and just this winter replaced the autopilot. I don’t remember exactly, but I don’t believe there should be any interconnect of the power between the acu and the sea talk buss. I would review the wiring at this juncture carefully. Also there is a fuse in the acu . Is that still good? It should have blown before your smoke occurred.
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