Contour Enthusiasts Group Archives Forums Modifications Audio Fuse placement/ratings?

I have a 400W amp w/ crossover that I'm powering through 4AWG cable running from the battery. The wiring kit I bought came with a 150 amp fuse for the fuse holder by the battery. The amp is equipped with three 25 amp fuses (75 amps total?).

The manufacturer says that I should use an 80 amp fuse by the battery, and another 80 amp fuse right in front of the amp (after the distro block). Does that sound right? Wouldn't it be safer to put a 70 amp fuse right before the amp, so that it blows before the fuses in the amp do? Or would that be too small and blow all the time?

i would imagine just go with the setup they sold in the wiring kit, they wouldnt sell it if it didnt work.
thats the way i have it set up is the main fuse near the battery, two smaller ones in each amp

When in doubt, always go with a fuse rated lower. That way, you blow a fuse way before you blow an amp!!! I'm not sure how many amps the fuse under my hood is but I know that 70 or 80 amps in the dist box sounds way too high! How many power lines are coming out of your dist block? I have 2 amps being powered and each one has an oversized 20 amp fuse. Also, amps often blow up without anything happening to those mini fuses in them so dont rely on them to protect your system!

Well, the amp has three 25-amp fuses, which the manufacturer says equals 75 amps. 400W=I^2*4Ohms, so I (current in amperes) is 10. However, I chose computer science over electrical engineering, so I'm not really sure if this works here. How many watts are your amps?

There will be two lines out of the dist block: one 4AWG for the amp, and one 8/10AWG for the crossover. The dist block itself doesn't have a fuse, so I was planning on splicing in my own right before the amp.

That helps a lot. My dist block has fuses in the middle. It has receptacles for 2 4ga power wires in and 4 4ga wires out. In the middle of the block are fuses. I have 20 amp fuses in there. Like I said in the earlier post, when in doubt, use lower rated fuses. The worst that will happen is that you blow more fuses. You don't want to start letting too much current get through and fry your amp. Just put a 20-40 amp fuse in between the power coming out of the disti block and the one going into the amp and you will be good!

Never repeat this line again. Amps FRY due to LACK of power/amperage. If you dont want the amp to receive the proper amount of current that THE AMP is DEMANDING (the amp creates the current draw, it wants power) Then you could use 10ga wire. No need for fuses, the wire would limit you. (and melt to a crisp in the process)

The amp kit you bought probably has an ANL inline fuse holder. Simply buy a 80 amp fuse (it is the correct size, the maunfactures do rate things like fuses correctly) NOTE: I am assuming that this is your ony amp in the car. In the distibution block, 80 amp fuse would be the way to go as well. Putting a 20 amp fuse on a amp with 75amps of total current draw (assuming the amp will require this current) is simply a waste of fuses.

The fuse included should be fine, the fuses in the amp will blow if there is a surge or something. Thats what i always thought anyways, werent the fuses by the battery just incase the power wire grounded somewhere or osmething than itll just pop the fuse preventing any damage done (ur car melting up lol)

After talking to a couple of friends who've done this a lot more than I have, what you say makes sense. You're right: the kit came with a 150A ANL fuse. I replaced the 150A with an 80A by the battery. I may put another 80A before the amp, but I was told its just a waste of money, as the first fuse should protect the amp from a short in the line.

I still need to put a 3A blade fuse before the crossover, since it doesn't have any fuses built into it.

Thanks everyone, I'm learning as I go.

The fuse in the back of the car protects the wire going to the battery. Incase you do have a short, the fuses in the back are usually a lower amperage (not in your case) On a dead short its still tough to blow higher amp fuses (I had a battery in the rear fall over and not blow a 200 amp fuse) It is just a safety precaution. If you had more than one amp then a fused distribution block would make sense, but with just the one amp you should be ok.