Wiring amp through fuse box or firewall? (1 Viewer)

Well, I've got my box built etc, and now it's time to wire.

I've got a ~300W infinity amp in the trunk that's gonna power the 12" inf. sub. What I don't know, is whether it's better to wire power from the battery or from the fuse box.

I'm leaning towards the fuse box, cuz it's easy to get at and it just seems like a "cleaner" way to do it. (I'm in a 2001 corolla)

Does anyone have experience with that?

I just spent half a day fishing two 8 gauge cables through the firewall of my jeep to run two amps in the trunk space. It may have been easier to run them from the fuse box inside the car but there was nowhere in the fuse box to tie in a cable of that size or to mount the 40 amp fuses which are far bigger physically than anything in there already. Everything I looked at for advice (never having done it before) said to wire it straight from the battery and have an in-line fuse within 8 inches of the battery connection.

If that amp goes bad or you get a short in the cable I would want that fuse to blow and not affect any other circuits going through your main fuse box. Remember if your average running watts, or rms, is 300 watts you are going to be drawing around 21 amps and a lot more at peak outputs.

i wrote a tutorial in here, that i hope someone looks at sometime :frowning: it covers some of what you might be looking for... DO NOT WIRE THE POWER WIRE TO YOUR FUSE BOX!
Wire it straight to the battery and make sure the fuse is no more than 6-8 inches from the battery terminal. No exceptions, this is how your power wire should be wired.

prop up

Thanks guys, sounds like I will be goin through the firewall then.

I have a hunch there's a hole I can use with the power brake, but if not i'll be breakin out the drill haha.

just make sure to get a rubber grommet that fits snugly to protect the wire from chaffing and shorting, and to protect your interior from water

I just generally punch an x through the grommet

if it is small enough to make the wire fit snug, that is a good way to do it, just possibly throw some sylicone sealer around the wire for water protection. if you drill a hole, again, get a grommet!

Under no circumstances should you use the fuse box. The grommet is a must. If you have an old antenna laying around take it to a bench grinder and make the ball into a point then you can push it through (do not force it or poke into harnesses) an existing grommet and into the car. Once you find a suitable grommet take electrical tape and tape the wire to the antenna and push it back through the grommet and into the car. Make sure to seal the wire even if it is in a rubber grommet to guarantee no leaks.

Something to add to this that everyone may find helpful. I've been installing for about 11 years, and a majority of them in a professional environment.

I've found that if you need to punch through a grommet, you can use the cigar punches to good result. They can be picked up for around $10-$12, and cut a perfect circle in the grommet.

Still a good idea to add some silicone once it's done though.