Melted power wire

I was taking my equipment out of my truck to take it to the shop and I pulled the inline fuse under the hood. I noticed that the clear plastic fuse holder was cracked the power wire after the fuse was all brown and looked like the outer cover was starting to melt. The only thing I can think of is that the fuse is too big for the power I'm running. I'm running about 500 watts rms 800 peak on a good day. And the fuse is a 50 amp. Is that too big or what else could have caused that to melt? I thought the fuse was supposed to blow before anything melted or shorted out. :uhoh:

what guage wire?

4 maybe?

I had to go find my old amp kit box. It was 8 gauge and it originally came with a 60 amp fuse, so I must have picked up a smaller one somewhere. Is 8 gauge too small? When I first started building my system I asked the guy at mickey shores and I told him everything I had and he said that should be good. On the outside of the box it says up to 300 watts. So If my amp is 760 max I should still run under 300 rms. Right?

How far is your fuse from the battery?
8g power wire is fine if you're only running 1 amp thats 300rms. If I remember right, I had a 40amp fuse with my 8g wire. I was running like 400 maybe 500rms w/o any problems. I've heard of that when you overload a wire like my friend did running 2 amps off a 8g wire. The whole thing melted and blew the fuse.

the fuse holder was 6 inches at the most from the battery.

an 80A fuse may be a bit too big for an 8 Ga wire.

shit, my 4ga has a 60 amp fuse

No. the amp kit came with a 60 amp and when I pulled it apart the other day I had a 50 amp in there. So it should have blown sooner.

maybe it melted from engine heat

thats what i was thinking

I would have to doubt that. Who ever make the wires knows it has to connect to the battery, which is under the hood and they should know it can get hot under there. Plus were it was burnt was right on top of my radiator resivior. And that was plastic so if the wire melted I think the plastic resivior would have melted first or looked discolored which it wasn't. And the whole wire wasn't burnt. Only about 3 inches right after the fuse holder.

Hmm. 8 awg should be able to take 50A (I've done it). I'm stuck.

Your ground might have something to do with my friends ranger melted the power wire about 6 inches and it was becasue his ground 3' long. Made it 6" long and he hasnt burnt it up since. Either that or you have to much power running through the wire.

The amp is in the extended part of my truck right under my enclosure. And the ground wire is only a foot long at the most. I un-bolted the seat and sanded the paint off and bolted it back down, so it should be getting a good ground.

Sounds to me like your ground wire hit your power wire while it was connected....

If it shorted out to ground shouldn't it have blown a fuse? Either the inline fuse or the fuse in the amp. Right?

Sounds to me like your power cable is not big enough. I've had a lot of experience with undersized cabling melting because they get too hot from the load they are carrying - especially near any lugs or terminal joints.

The other point is - can the lugs/terminals joining your power cable to the fuse carry the current required without getting excessively hot?

Also your plastic reservoir would have a far higher temperature rating (being designed for an engine bay) than the insulation on your power cable.

My :2cents:

fusion brought up something I hadn't really thought of ...... most of the resistance in your power wire is caused by the connections. If they are not real tight and solid electrical connections, they will heat up the quickest.

That does make sense because to put the fuse holder in line you have to cut the power wire and twist it then use the set screw to hold it in there, and the set screw does spread the wire a bit. So what do you think should be done? Maybe drip a bead of solder onto the wire to hold it all together?

get wires that that fit tight into the holder, and make sure the connection is tight

I agree with PaulD - match the size of the terminal to the wire gauge to prevent spread and maximize contact. Try to avoid solder - it creates high resistance.

.....Try to avoid solder - it creates high resistance.

BULLSHIT!!!!!!!!!!!!!! Soldering all your terminals together would probably be the best thing you could do for the power wire connections. Soldering does not cause resistance, it decreases resistance, and it doesnt have as many problems when it starts to corrode. You have no idea how stupid that made you sound by saying that. Whenever I add or repair any electrical connections in my car, I always solder. If you dont know what your talking about, dont talk. Thankyou

Thanks for the postive comments.
I know exactly what I am talking about. I take it your an experienced electrical engineer then?

anyone else care to comment on wheather soldering decreases or increases resistance in wire connections? So I suppose just crimping them is way better than soldering. Ok, you do what you want, and I'll continue to solder.

I was referring to soldering before placing the bare wire inside a terminal. As we were talking about hotspots I think this is quite relevant. The increase in resistance from the solder can cause a hot point. This is what we are trying to help OffRoadSonoma avoid.

You might find solder has a higher resistance than copper wiring..

Please inform us all how solder decreases resistance?


Soldering after should have no effect on resistance as your "bare wire to metal terminal / crimp" contact is already made. It is just for mechanical strength.



So sorry to OffRoadSonoma for arguing in your thread.

I trust we have been of help to you. Please tell us how your wiring has come along.

Yes, You all have been a help. I took that setup out of my truck and I'm selling the truck. I'm gonna put a new setup in my current car and run 0 ga to hopefully avoid this problem. Thanks for all the coments.

I see where your coming from, and I'm sorry to be so negative. I usually put the bare copper wire in the connector, crimp it tight, and then solder it together. This may not desrease resistance, but from what I understand, it creates almost a chemical bond, much like welding, which if it corrodes, will not increase in resistance as much as just a crimp connector alone. Thats what I thought you mean by soldering. I didnt know you meant just soldering the wire alone, and then crimping it down in a connector. I can see how that would cause resistance, but I know crimping it and then soldering it would not.