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A couple days ago, I noticed the voltmeter in the cockpit reading low (below 12 volts), then I noticed that battery 1 (which I use to run lights, electronics, etc.) was quite low (11.8 volts on the multimeter).
Upon inspection, I found that the fuse on the line between the alternator and battery had blown or somehow smashed, as the glass was broken. I replaced the fuse (30 amp, 32 volt) and turned on the engine. The voltmeter on the cockpit jumped to just over 13 and seemed to be slowly rising for ~10 seconds, and then the fuse blew again. I cleaned and tightened the contacts on the wires. Put in a new fuse, tried it again - same exact thing happened.
I did the alternator test shown here (
), and it seems to indicate that the diodes are fine.
If I put a wire with clamps from the alternator post to the battery (small wire, not doing it for any extended period of time, just to get readings), I get 13.1 volts at the batteries, 13.1 (approximately) at the cockpit voltmeter, and 15.3 volts at the post on the alternator using the multimeter.
The alternator is rated at 51 amps, and is fairly new, but was on the boat when I bought it. Is it possible that the 30 amp fuse is a remnant of the old system, and I need a 50 amp fuse for this alternator?
Recently I've been using the electric system more (just installed pressure water, anchoring out more w/ anchor light on, running an inverter to charge a drill occasionally, etc.), so maybe I've just drawn down the batteries to where the alternator is kicking into higher gear and blowing the small fuse? Not sure if that's how the regulator works, but it could explain why it's been fine and hasn't blown the fuse until recently.
Any help appreciated!
Upon inspection, I found that the fuse on the line between the alternator and battery had blown or somehow smashed, as the glass was broken. I replaced the fuse (30 amp, 32 volt) and turned on the engine. The voltmeter on the cockpit jumped to just over 13 and seemed to be slowly rising for ~10 seconds, and then the fuse blew again. I cleaned and tightened the contacts on the wires. Put in a new fuse, tried it again - same exact thing happened.
I did the alternator test shown here (
If I put a wire with clamps from the alternator post to the battery (small wire, not doing it for any extended period of time, just to get readings), I get 13.1 volts at the batteries, 13.1 (approximately) at the cockpit voltmeter, and 15.3 volts at the post on the alternator using the multimeter.
The alternator is rated at 51 amps, and is fairly new, but was on the boat when I bought it. Is it possible that the 30 amp fuse is a remnant of the old system, and I need a 50 amp fuse for this alternator?
Recently I've been using the electric system more (just installed pressure water, anchoring out more w/ anchor light on, running an inverter to charge a drill occasionally, etc.), so maybe I've just drawn down the batteries to where the alternator is kicking into higher gear and blowing the small fuse? Not sure if that's how the regulator works, but it could explain why it's been fine and hasn't blown the fuse until recently.
Any help appreciated!