So this shitbox Subaru I bought has been nothing but trouble. It was giving me all the signs of a failing alternator, the lights would get brighter when I gave it gas, it died if I pulled a battery cable when it was running, etc. So fine, I put a new alternator in it. It was fine for a while, then one morning it wouldn't start, so I jumped it and put the battery on the charger all day at work, and it was fine for about a , week, when it wouldn't start again. Charged the battery again, this time it only lasted a few days. Eventually I was charging it every day only to have it nearly die before I got back to work the next morning. I took that, along with several people confirming it, to mean the battery was just really, really dead, so I just put a brand new battery in it, and it was fine all weekend.

Today, my windows were frozen, so I started it and let it run for 10 or 15 minutes with the heat and defrost on full blast, and when I got back out there, it was putt-putting pathetically, missing like it had been right before it died. I got inside, and the dash was ablaze with all the warning lights on, like it had been right before it died. I turned on the dome lights, both map lights, headlights, and radio to check, and all the lights were really dim, and each new one I turned on made the others dimmer. The radio came on for maybe 15 seconds then shut itself back off. I made it to work, but by the time I got there it had no power and was missing like crazy.

Thoughts? I thought I might have just gotten a bad alternator, but it keeps running when I pull a battery cable, even with the headlights on.

So now I'm thinking I didn't need a new battery in the first place, but before, it wouldn't start, then after I charged the battery, it would. I'm not leaving my lights on or anything. The ground looks fine, not rusty, the battery cables aren't frayed and are tight, and they're not corroded. What the hell could it be?

tl;dr 1990 subaru legacy something is wrong with my electrical system that's not the alternator or battery or cables.

I would check the cables again. Cut some insulation off and look for the green. That or themain harness. Seems like the charge isn't getting back to the battery

this is going to sound dumb, but check your body and engine grounds for corrosion.
seen it happen a couple of times with other makes.

Check your interior for orbs.

Posted by Samurai this is going to sound dumb, but check your body and engine grounds for corrosion. seen it happen a couple of times with other makes.

Grounding issues can cause you to pull your hair out. Definitely worth a check!

I'm 100% sure its the engine ground...I have dealt with this same issue.

I took off every ground I could find coming off the battery, cut them back, exposed new copper and put new connectors on them, and scoured them with a wire brush before putting them back on... Hopefully that works, it wouldn't start but I figure my battery has got to be dead by now so I'm letting it charge for a few hours. Thanks for the suggestion, I'll keep you posted.

If this doesn't work, I'm thinking new terminals on the battery cables next? They don't look particularly bad, but they're certainly old.

Posted by CDSbigsby I took off every ground I could find coming off the battery, cut them back, exposed new copper and put new connectors on them, and scoured them with a wire brush before putting them back on... Hopefully that works, it wouldn't start but I figure my battery has got to be dead by now so I'm letting it charge for a few hours. Thanks for the suggestion, I'll keep you posted. If this doesn't work, I'm thinking new terminals on the battery cables next? They don't look particularly bad, but they're certainly old.

What about your engine block ground?

Posted by Agent Skelly What about your engine block ground?

I initially missed it, after I did all the other ones I put the freshly charged battery back in and let it run with every electrical thing I could find turned on and it died again after 10 minutes or so. So I went back to see if I missed any and I saw that one, so I redid it, but then the battery was dead so I couldn't test it, I'll check it tonight.

Well, that didn't work.

K, so, I pulled the alternator and got it tested at O'Reilly's and they confirmed it is working fine. The battery is new, and I'm fairly certain it doesn't have a dead cell or anything, because it acts the same with the new battery as it does with the old one.

This brings us to the wiring. Am I correct in thinking that because the car will start, and run, and power all the lights and whatnot for a while, then it dies, this means the problem has to lie with the wiring coming off the battery's negative terminal?

Because I already cleaned all the connectors but now I'm thinking of just buying new wire and completely re-doing it to be sure.

The only other thing I can think of, on the new alternator where the wires plug into, the plug that goes in has 3 wires going into it (yellow, black, white) and it has 4 holes for pins. Only 3 of the holes have pins in them, one to each wire. However, on the alternator, it has 4 pins, one of them goes into the empty socket on the plug. Could this mean they gave me the wrong model alternator? Is it maybe not working right because that alternator is supposed to have another wire coming off of it to do something?

Is your belt tight enough? I had a situation with a Dodge where the belt wouldn't squeal or anything, but it'd slip on the alternator pulley and act like it had a bad alternator.

Also, does this car use a relay for the charging system? It could be sticking open.

Posted by CDSbigsby The only other thing I can think of, on the new alternator where the wires plug into, the plug that goes in has 3 wires going into it (yellow, black, white) and it has 4 holes for pins. Only 3 of the holes have pins in them, one to each wire. However, on the alternator, it has 4 pins, one of them goes into the empty socket on the plug. Could this mean they gave me the wrong model alternator? Is it maybe not working right because that alternator is supposed to have another wire coming off of it to do something?

It's probably for some separate options package but still fits your car- I've seen this on a lot of different models.

Something that hasn't been mentioned yet:

Bad voltage regulator somewhere in your wiring loom.

I had this problem on my '67 SAAB (way simpler electrical system obviously, but still...).
The battery would die overnight. I wasn't getting the "alternator not charging" light on the dash, so I knew it was OK. Got a new battery and didn't fix it. Only sign something was wrong (other than the power drainage) was how my electric fuel gauge would always read 1/2 tank when the ignition was OFF.
I pulled my hair out for weeks, then broke down and took it to a local Saab dealer who had experience with the old models. Turns out the old Bosch voltage regulator had gone bad. $68 dollar part that they still made (thank God) and it was fixed.

Might wanna look into an in-line regulator somewhere... (I won't profess to know how to check its functioning though)

The voltage regulator is built into the alternator from what I've heard.

And I'm not sure if there is a relay, I'll check into it. There is a fusible link for the alternator, but it doesn't look to be burned through...

I got all new wiring, connectors, and a battery terminal, and wired up a replacement for the negative cable and all its grounds. We'll see if that works.

Nothing's worked so far.

There's a fusible link for the alternator in the fuse box, it doesn't look burnt, but I was going to replace it just to check, thinking it'll be a couple bucks...well...Advance Auto doesn't carry them, he said it's a dealer only special order item and then it would probably be like $100.

Beyond that, the only other thing I can think of to even check is the hot wire for the alternator.

Posted by CDSbigsby Nothing's worked so far. There's a fusible link for the alternator in the fuse box, it doesn't look burnt, but I was going to replace it just to check, thinking it'll be a couple bucks...well...Advance Auto doesn't carry them, he said it's a dealer only special order item and then it would probably be like $100. Beyond that, the only other thing I can think of to even check is the hot wire for the alternator.

Just jumper it with a penny

Well, I'm going to try jumping the fusible link with some wire, and if that doesn't work, I'm throwing in the towel and selling the piece of shit off for whatever I can get out off it.