Alternator wire fried

[Wizard]

Okay, so I'm driving home in my 96 legacy and see my speedometer and tachometer drop to zero then when I step on the gas it comes back. Then the radio goes out. So I recognize the symptoms of a dead battery. Get to the top of the driveway and the car dies. I'm pretty sure I know what I'm going to find under the hood because This is the third time in 1.5 years that this has happened.

I haven't ever figured out where that wire goes but I'm assuming it goes to the battery because it's connected to the alternator. The wire gets fried like that about every 6 months then I re-attach it and it's fine until it gets hot and fries itself again. I thought maybe it was a bad alternator but the last time I took it out and got it tested and it was fine. I'm thinking there is a deeper problem here though. Some thing is overpowering that wire(obviously) maybe someone here would know what's going on. And why is it so regular. Regular to the point that last week I checked the wire to see if I could tell if it was going bad. I couldn't tell anything so I just kept driving and now it happened again.

 

I don't remember the check engine light going on the other times, maybe I didn't check the codes and maybe it was never on in the first place but this time it is on and so I checked the codes and I'm getting

po500: the speed sensor is at fault

Po135: the bank 1 O2 sensor 1 oxygen sensor heater circuit

Po180: the bank 1 O2 sensor 2 oxygen sensor heater circuit

 

I haven't done any research on what the last two are so I have no idea what that means but I guess it makes sense that this problem has to do with a heater circuit. Any ideas on how to figure out what's up with my subaru?

[matt167]

That is the positive feed to the battery. The other end bolts on to the battery cable near the battery. Run a new cable from where it bolts up. It's damaged, draws too much current and burns up.. You can use lawnmower battery cable as a quick and easy fix. Sold everywhere including Walmart and is has ends you can use on it for both ends

[Bushwick]

Do you have anything aftermarket in the car? Like add-on fog lights, a car amplifier, etc.? 

 

 

I've never seen a charge wire do that on it's own. It's EXTREMELY dangerous though, like car on fire dangerous.

 

 

It's possible the connection had a build up of acid? (the green stuff that looked like mold that used to end up on battery cables). Over time, it'd eat the cable, and the current would eventually be too much, and the wire will come apart.

 

Normally I'd recommend replacing the entire cable with brand new, then monitor it daily. By monitor, get out and see if the rubber is melting or getting excessively HOT (alternator itself will cause a bunch of heat to enter the cable, you need to be concerned if it's ruining the integrity of the actual wire or not), but considering the nature of a possible car fire in the future, I'd have it towed and professionally inspected for your safety. I'm just a DIY'r.

[Fairtax4me]

Just a poor connection there. If it burned once and the end of the wire was just cut and a new eye terminal installed that's not good enough. Heat damage to the wire lowers its current capacity, which in turn increases the heat buildup in the wire. The game is current vs resistance vs contact area at the crimp. Small contact + more current = more resistance, more heat.

 

 

That wire runs to the bottom of the fuse/relay box and connects underneath it.

I don't remember if there should be two wires or not. At this point it's best to replace the entire wire from the alternator to the fuse panel.

As mentioned before, any aftermarket accessories, big sub and speaker amps, etc., will increase current draw through that wire, and the size of the wire needs to be increased to allow for the higher current load.

Lastly, make sure your battery connections are clean and tight, and the power wire from the battery to the fuse panel is in good shape at both ends. And make sure the battery is holding a proper full charge. A battery that cant hold full charge is dying and will cause the alternator to have to produce more current trying to recharge the battery. A good battery will show at least 12.4 volts after sitting for 12 hours. Ideally you want 12.6, but anything below 12.4 indicates either the battery is not getting a full charge, or that it is discharging itself and is not holding its full capacity.

[Wizard]

There have always been two wires since I bought the car but that also doesn't mean that it is the way it's supposed to be. Any idea what gage that wire is? It looks like 12 or 14 gage to me. There is an aftermarket cd player in the car and I have always suspected that the speakers are aftermarket because they are too good to be 21 years old. So it could be just slightly too much current going through those wires. We will see when I switch them out for bigger wires. Thanks for the help!

[Wizard]

So took off the wheel panel that protects the wires from getting muddy and found a big bundle of all sorts of wires. I didn't really want to take it apart because I didn't know if I could get it back together again but I couldn't be 100 percent sure that the two white wires that go into the fuse box were the same white wires to the alternator. So I unplugged the wires from the fuse box and tried to do a volt test by connecting the wires from the alternator to the battery. I thought it would be an incomplete circuit and not do anything because it was unplugged at the other end but it did complete the circuit. So is there a portion of the wire that is bare in the bundle of wires that is above the wheel that I can't see? Or is the circuit complete even if it's unplugged? Or are those two white wires that connect to the fuse box not actually what I

[Fairtax4me]

I don't follow you.

The wires are disconnected? But you're testing for voltage on them? Why?

 

I remember now there are two wires because they go to two different terminals under the box. Im not sure why because I'm pretty sure they both connect back to the battery supply post inside the box.

 

They might say which size they are on the insulation somewhere. Probably 10 or 12.

Try cutting that back about 6" from the burned end and see if the strands in there are discolored or corroded. If the copper is clean you can solder new ends on and solder them to a new eye terminal to go on the alternator. Be sure to heat shrink over the connections.

[Gloyale]

the 2 White wires at the Alt splice toghether and go then through the fusible link in the box.

 

The other 2 wires are: 1) a tap off the 2 merged ALT output wires going into a Slow blow fuse block 2) the other side of the SBF coming out and on to main "BATT" circuit to the interior fuse box.

 

Your problem is almost undoubtedly that wire fusible link.  replace it with a 2 Inch section of 12 gauge fusible link wire.

[Bushwick]

Your CD player should be fine. What I was referring to was an external amplifier capable of demanding more current than the alternator can supply. 

 

If you are attempting the repair yourself, might as well add a couple extra redundant ground cables. One from engine to firewall/body, and another from battery to firewall/body. If a main ground is bad, it can cause hot wires to crap out. I've seen starter wires cook from poor grounds before.

 

Again, not something you want to keep dealing with. If a live cable from the battery touches ground while the car is sitting overnight due to a future break, it can cause a fire.

[Mike104]

One option is to go to a pull and pay yard and take the alternator cable from a similar car (Check for corrosion on the terminals)