Fuse Blowing..help?

Hi all,
We just got our wakesetter back from the shop and its running good now. Up until two days ago, the speakers were working great, but all of a sudden, our subs quit working. I don't know a whole lot about the flow of electricity, so I am hoping someone can help me out. Here is what I found. The fuse that is in the holder from the battery to the Amp has blown out. I unplugged the power and ground from the amp, then reconnected it. I replaced the fuse. so far so good. I turned on the stereo and instantly, with the sound turned very low, the fuse blew again. It can't be that its too loud, because i had it turned down to like 5 on the volume. like I said, i don't know much about how electricity works and flows, but maybe there is too much power shooting to the amp?? Anyone have any ideas? Let me know, thanks.

Jeff, are your batteries charged up? Low voltage will cause the cables/wires to pull more amps to get the same power. This is why having a charging system with low voltage can really hurt you in ways besides not charging your batteries. Low voltage will shorten the length of electronics, lights, etc.

Just a thought. If that is not the problem make sure the jacketing of the cables from the batteries to the amps aren't cut open allowing the power to ground out and blow the fuse.

Hey Brett,
Pretty sure the batteries are charged up. We have two batteries with a switch and have been running the boat regularly, so they are getting charged up everyday. I will check the power and ground cables from the battery to the amp and make sure they aren't cut open. They shouldn't be because its all new wiring..but you never know. Any other possibilities? I find it weird that it was working great for about a month before this problem started happening.

What size fuse did you install?

How many watts is the amp?

It is possible that the fuse is just too small for the load. Keep in mind that the fuse's job is to protect the boat, not the amp. The fuse should be sized large enough for what the wiring can handle, which should be significantly more than what the amp would draw.

Brett's comment regarding less voltage = higher current is true with respect to the amp, but not to most of the boat's electrical system in general. The wiring and fuse should be sized to handle the worst case current draw from the amp and if it is appropriate then the battery voltage would not be an issue.

If the fuse is a proper size then my guess is that the amp itself has failed and as soon as it turn on it draws excessive current. I have had amps fail this way before.

It may be time for a new amp.

Rod

Make sure everything is grounded properly

Rod- I have a feeling it may be the amp that is failing. It is an older amp and i wouldn't be suprised if its doing what you have described. I am not sure the size of the original fuse that was in there when it was working fine. But i went to the store and bought a couple extra to mess with it and i bought 60w fuses. The amp itself, i believe, is a 600w amp. I will take the amp out of my car, test it in place of the one in the boat and see if that works. Thanks for your help. If any info i provided sparks any other thoughts, please let me know. thanks again.

I run 80w fuses to my system. at the sandbar on hot days they will blow when my jl 13w7 is blasting for extended periods. I will open the passenger side/ battery compartment hatch and move towels/bags/cover/etc to make sure to get adequate airflow to the amp. They will get HOT and become more easily blown. also make sure all your connections are tight. (battery terminals:both battery posts and wire to terminals, also on your engine itself: negative post on engine, positives on starter.) good luck I would start with bigger fuses and don't forget a pack of spares in the glovebox.

I don't think low voltage could ever cause a fuse to blow. Fuses blow due to excessive current which causes the fuse to over heat then burn. Current equals voltage divided by resistance. So let's use small easily divided numbers. Say you go from 12volts with 6ohms. That's exactly 2 amps. Now you go to 6volts(battery needs charged) with the same 6 ohms resistance. You went from 2amps to 1. That's less current and less heat which means your fuse is less likely to blow. If fuses are blowing it's either something wired wrong and shorting to ground or damaged wires shorting to ground. Or it's a bad component, most likely the amp drawing too much current. It cannot possibly be too low of a voltage. But then again I'm just an aviation electrician/electronic technician and don't know that much about audio systems.

Also even if the system's trying to draw more current to get the power up to par. Power's current times voltage. Powers also what causes the heat. So say your system's drawing two amps instead of one to offset your 6 volts vs. 12. You're still coming up with 12 watts and dissipating the same amount of heat. Obviously you're getting more than 12 watts I just used those numbers to make the math simple.