Alternator not charging

[Hondamonster]

Facts: 89 carbed

-Battery light stays illuminated with the engine running, indicating a charging problem.

-The battery is brand new with a full charge.

-Checked the underhood and under dash fuses, and they all check out.

-Removed the alternator and bench tested it at work (autozone) and it tested good, 14.72 volts, all other parameters in spec, 6 times in a row.

-Re-installed the alternator, started the car, still not charging. Checked voltage at the big white wire on top of the alternator with the engine running and found 0 volts. Also 0 volts with the car off and key in the on position.

-Grounds are solid and clean

-The black/yellow wire and white/green wire in the green connector on the back of the alt. (to the voltage regulator) both have 12 volts with ignition on engine off.

-Tested the white wire again, still getting 0 volts in all conditions. So I traced it back through the harness and found it ends in a metal relay looking thing. From researching on here, everyone else seems to think the white wire should go directly to the fuse box. The fuse box does have a big white wire going into it, but it doesn't trace directly to the alternator. I haven't changed any of the wiring from factory as far as the charging system is concerned. no splices, butt connectors, etc. Everything seems to be plugged up and connected well. Grounds are good, etc. So should I just put the big white wire into the main power circuit or what? Any ideas of what that relay is? Or suggestions that could point me to why it isn't charging?

[2oodoor]

I think that goes to the underhood fuse box to one of the funny looking fuses, 40 amp or higher.
I accidently touched that white wire to ground one time and it popped that fuse. That is not a real popular fuse at parts stores but pep boys has them. I get them from the junk yard.
I think you may be able to touch top of the fuses at the exposed metal with a test light to check. Do both sides of the fuse.
Also I had a phantom issue that turned out to be black goo inside the battery terminal ends preventing good contact.

[poorman212]

There is also a 10amp fuse (no 8??)in the underhood fuse box to check

[Hondamonster]

I checked all the fuses. Under the hood and under the dash. I think I'm going to route the white wire directly into the power wire and see what happens.

[2ndGenGuy]

I've had alternators that tested okay, but still wouldn't charge in the car, and a new one fixed the issue. I don't know if the testers at the parts stores put a proper load on them or not. Anywho, just my experience. Might try a known good one and see what happens.

[Dr_Snooz]

The manual has an excellent set of charging system diagnostics starting on p. 24-20.

[Hondamonster]

Yeah I read that whole thing and did every test (besides the internal alternator tests) that it mentions. I figure the bench tested the whole alternator and it was good so there's no reason to test individual parts of it. Anybody know what that metal relay is before I bypass it?

also, if somebody could test voltage at the white wire on top of the alt with the key on engine off, I'd really appreciate it.

[mushroom_toy]

I've had alternators that tested okay, but still wouldn't charge in the car, and a new one fixed the issue. I don't know if the testers at the parts stores put a proper load on them or not. Anywho, just my experience. Might try a known good one and see what happens.

I told him the same thing.

But yeah not getting 12v at the wire would be the problem....i would still change the alt though.

[Hondamonster]

Got it.

Alt was fine just like I said. Went ahead and bypassed that white wire entirely and ran a new one from the alt to the power wire and everything works fine. go figure. such an oddball problem to just randomly occur, but just thought I'd say its all taken care of

[ShyBoyCA6]

i have a similar problem but everything will light up like it was normal but no start. i jump started the car and stayed on but didn't die. the light will come on when i press the brake pedal or when im stop at a red light for a bit. when im driving it goes off. i haven't checked the fuses yet but will get to that. also my alternator is making a loud whining noise don't know what that means (maybe brushes are going bad). Anyway my question is can we use a different alternator with a bit more amp? i read on here someone using 70amp alternator but didn't say from which car. also someone else on here is using a civic alternator? im not sure? any help on this question would be great thanks all!

[import racer]

I had an alternator from a civic on my 87 hatch,it was new just before I junked it.Only thing I changed was top bracket,got one off small block chevy.I shortened it and drilled a new mounting hole.