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Old 01-02-2003, 12:29 AM   #1
atomicapples
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Default power wire produces heat?

well i am relocating the battery, and its a 2 guage wire.

im running along the driver side. but im wondering if it will produce heat. its running along fuel lines. if im not mistaken.

i dont want to start a fire not risking my car to blowup.

thanks

tony.
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Old 01-02-2003, 01:25 AM   #2
tdxflex
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don't think it will give off much heat. usually they put enough insulation, on my old car i had 4ga wire for my stereo and it never really even got warm. use some flex tubing from home depot if you're worried about it.
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Old 01-02-2003, 02:27 AM   #3
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4 gauge is OK for car stereo as it rarely requires more than 30 amps.

However for a battery relocation, even 2 gauge seems small to me. If it produces heat, it's too small ! I used 2/0 gauge in my previous car and I was OK. Remember that you want to be able to recharge the battery. Dunno about the REX but VW alternators pushed 90 amps. It's a lot more than a car stereo ! Better be on the safe side.

My 0.02$
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Old 01-02-2003, 03:12 AM   #4
teiva-boy
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I think the wrx was around 65amps but no more then 75amps from the stock alternator. The RS has a stronger alternator.

2ga is fine. But like the advice for fueling where you can never have enough... Same goes for wire. Dont skimp.
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Old 01-02-2003, 03:53 AM   #5
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2 guage will be fine, it's not going to heat as you will never crank your car long enough to get it hot. you max current draw will be when starting and it will most likely peak @ about 150amps. what you DO need to remember is that the smaller the guage wire the more resistance it builds over a distance, that's why they reccomend lower guage wire for heavy high load travels. as far as i am concerned i think you'll be fine. Just remember that teh factory harness are 4 guage IIRC.

jeremy
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Old 01-02-2003, 12:16 PM   #6
tdxflex
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i also agree that 2ga will be fine. Ti-REX, i was actually pushing 80-90 amps with my stereo and the wire held up fine and didn't get warm to the touch. 1/0 would be better because of the resistance that HndaTech touched on, but the internal resistance of a battery is tiny, added to the length of wire's resistance, is still very small (relative to other electrical devices in your car). just make sure you put a fuse or a circuit breaker as close as you can to the positive terminal.
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Old 01-02-2003, 03:49 PM   #7
atomicapples
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so i should put a fuse in the middle of the power line from the battery to the distribution block that then goes to the starter and accessories line?
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Old 01-02-2003, 05:11 PM   #8
tdxflex
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yeah, the fuse/circuit breaker should go as close to the battery as possible for safety reasons and it's the law to have a fuse within 18" of the battery, so if for some reason say the wire gets cut at the firewall, or at the back seat, etc you minimize the chance of an electrical fire.
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Old 01-03-2003, 11:49 PM   #9
atomicapples
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Quote:
Originally posted by tdxflex
yeah, the fuse/circuit breaker should go as close to the battery as possible for safety reasons and it's the law to have a fuse within 18" of the battery, so if for some reason say the wire gets cut at the firewall, or at the back seat, etc you minimize the chance of an electrical fire.
sounds like a good idea. what size fuse? amp size?
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Old 01-04-2003, 12:22 AM   #10
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the size i'm not sure of. a long time ago i was asking questions about it and i remember one person was able to use a 150 amp circuit breaker. i would start there and if it keeps opening go up to a 175 or a 200.
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Old 01-04-2003, 12:40 AM   #11
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Default fusing

You have two lines you need to protect.

The main + battery cable you want to have a very high amp "SLOW BLOW" fuse. 150 A - 200 A sounds reasonable.

On the accessory wire most car manufactures do not use a fuse in the line but a fusable link. This is a section of wire abou 1 ft long that is 2 wire gauges smaller than the accessory wire itself. It is supposed to melt in case of a major short.

The largest fuse in the fuse box is 80A, most of the other large fuses are 30 A or there abouts. The point of the fuseable link is it will not blow due to minor problems, the fuses should do that. If you have a major problem the fusable link will melt close to the battery rather than have the main accessory wire start arching in some inaccessable place you can't get to.

They use the fusable link because it is not easily repairable, if it melts you need to find out exactly what the problem is and FIX it. People have a tendency to just slap another fuse in if it was fused and that could lead to a vehicle fire. Not a good thing.

Be very careful with routing for these two wires, they will be able to carry enough current to start a full fledged fire. If there is any place you even slightly suspect will abrade the insulation of the wire protect it very well.

This is the voice of experience. In my first hot rod, I had a grommet pop out of position on a major wire that went through the fire wall. I had been having odd problems for a couple days, head lights dimming momentarily etc but I couldn't find the problem.

I crossed a rail road crossing and saw a bright flash under the dash board closely followed by a cloud of smoke. Luckily I had wired the system with a master kill switch that killed all circuits except the ignition. I hit the kill switch, drove clear of the tracks then killed the ignition. That master kill switch saved my car. In that moment it was arching it burnt the insulation off of20-30 feet of wire under the dash board.


Larry
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Old 01-04-2003, 11:51 AM   #12
atomicapples
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Default Re: fusing

Quote:
Originally posted by hotrod
You have two lines you need to protect.

The main + battery cable you want to have a very high amp "SLOW BLOW" fuse. 150 A - 200 A sounds reasonable.

On the accessory wire most car manufactures do not use a fuse in the line but a fusable link. This is a section of wire abou 1 ft long that is 2 wire gauges smaller than the accessory wire itself. It is supposed to melt in case of a major short.

The largest fuse in the fuse box is 80A, most of the other large fuses are 30 A or there abouts. The point of the fuseable link is it will not blow due to minor problems, the fuses should do that. If you have a major problem the fusable link will melt close to the battery rather than have the main accessory wire start arching in some inaccessable place you can't get to.

They use the fusable link because it is not easily repairable, if it melts you need to find out exactly what the problem is and FIX it. People have a tendency to just slap another fuse in if it was fused and that could lead to a vehicle fire. Not a good thing.

Be very careful with routing for these two wires, they will be able to carry enough current to start a full fledged fire. If there is any place you even slightly suspect will abrade the insulation of the wire protect it very well.

This is the voice of experience. In my first hot rod, I had a grommet pop out of position on a major wire that went through the fire wall. I had been having odd problems for a couple days, head lights dimming momentarily etc but I couldn't find the problem.

I crossed a rail road crossing and saw a bright flash under the dash board closely followed by a cloud of smoke. Luckily I had wired the system with a master kill switch that killed all circuits except the ignition. I hit the kill switch, drove clear of the tracks then killed the ignition. That master kill switch saved my car. In that moment it was arching it burnt the insulation off of20-30 feet of wire under the dash board.


Larry
so the accessories line is made to just melt?

i think i might have that problem. but i wasnt able to find that problem. my car battery would die from time to time. that 80amp fuse has blown on me. and i just replaced it. after replaceing it it seems to be fine. but from time to time my battery would die. so i fugured it was a bad battery or something is draining my battery. bad ground?

so what is the best fix and the most common fix? replace that accessories wire?
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Old 01-05-2003, 08:14 AM   #13
hotrod
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Default sorta yes sorta no

Your not quite right.

The _fusable_link_ is designed to melt as a last ditch fail safe. It is a short section of wire (usually about 1 foot long right near the battery) that is a slightly smaller gauge wire.

I'm not sure if the subaru connector to the fuse box is a fusable link or not, but American cars have used them for years. They are usually a different color than the rest of the wiring. I consider them good practice in wiring if you are making a major change like relocating the battery.

If you have a massive short on the accessory wire, it will melt the fusable link before (hopefully) it starts a fire in some inaccessable location in the wire loom. Think of it as just another fuse, but it is intentionally designed to be difficult to replace -- this forces folks with a big problem to fix the problem not the symptom.

Like you said your self, you pop an 80 amp fuse and just replace it. Think about that for a moment, to pop an 80 amp fuse you had to have a load of over a 1000 watts some where in the system. Thats enough power to cook your dinner.

Yes if you have popped your main 80 Amp fuse more than once, you have a wiring problem you need to find and fix.

Dead battries can be caused by a lot of things, the obvious are lights left on.

The usual suspects are:
head lights not a problem on subaru because they are killed by the ignition switch.

stuck brake light switch or backup light switch, overhead interior light, parking light switch (the one on top of the steering column turned on by accident) or a door left ajar. Radiator fans switch sticking on, bad battery, dirty battery cable connectors, loose ground connections, or loose cable to starter.

Have you added any stereo equipment or done any other electical installs?

If you have did they all have fuses in the power lead?

If not they should be individually fused.

Is there any pattern to what you were doing the day before you had the dead battery?

Next time you have a no start condition, check to see if the battery is really dead or you are just having problems with the starting system like the clutch lock out switch. Turn the head lights on or the radio on, and see if either works with the key in the run position.

The most common causes for major shorts (the kind that will pop an 80 amp fuse) are melted insulation in a wire that passes an exhaust manifold, turbo, or cat, that shorts.

A wire that is rubbing against a sharp sheet metal edge like a hole in the fire wall with no heavy rubber grommet to protect it.

If you have wired in any accessory that passes a hot (12+ V) wire through a hole in the fire wall, that is the first thing I would check. Thats what nearly burned my car down. The edge does not have to be sharp like a knife either, just a bare metal edge will cut through insulation.

Custom lights are another common culprit. Have you installed High Intensity lights? Some folks have melted their head light wiring because of excessive power draw on those units.


Give us some more details on how your finding the battery dead, and what if any electrical changes you have already made, and we might get a clue to point you to a specific thing to check.

Larry
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