1989 Accord LX Charging System Issues

[Emonkey]

I have seen a few related posts on other sites but no answers. I hope we can figure this out.

The problem: Alternator not producing enough voltage to charge battery or keep car running (only ~12v)

What I have tried:
- Having alternator bench tested (twice) and it tests good
- Voltage regulator is internal and tests good
- Tested alternator while installed, and it does not produce enough voltage
- Tested the charging circuit up to the fuse box and found no continuity or ground issues

A clue:
- I accidentally left the #1 fuse out of the dash fuse box, and the car started but then died after a minute. When I replaced the fuse and restarted the car, the alternator was producing 14+v. Problem solved? No. The next day, I drove the car and ended up stranded with a dead battery. I tried the fuse trick again today, and it did the same thing.

Any ideas? Is this a relay issue? I don't think there is a computer in this car - it's carbureted.

Thanks!

[headbanger]

make sure that the post on the back of alternator isnt touching any metal had this happen once upon a time.

[Dr_Snooz]

If the alternator isn't producing enough voltage when the car is running, then it's no good.

[Emonkey]

Thanks for the replies.

Dr_Snooz, you're right. The alternator tested good at Autozone, but it wasn't. After confirming that I had 12 V at the alternator on the voltage regulator circuit, I swapped it out. Problem solved.

So, for posterity, the shop manual says to check for proper voltage at the alternator (to make sure there isn't a problem on the way to the battery). If the voltage is incorrect, then check for 12 V at the IG terminal (the plug with 3 wires coming out of it that plugs into the back of the alternator) on the black wire with a yellow stripe. If you have 12 V, your alternator is bad.

This seems to be a common problem with these alternators - testing good, but they're actually bad.

Thanks again.

[Dr_Snooz]

Take those Autozone tests with a grain of salt. Trust their alternators even less.

[Emonkey]

A sad addition to this tale.

I got a used alternator that tested good, installed it and it worked. When I first installed it, it was producing over 14V, but after several minutes it had dropped under 14V. It was pretty steady there and was enough voltage to charge the battery and stayed pretty steady when I turned the headlights on and such, so I figured it was good enough. After a few days of driving it, now the alt light is coming on (after about 3 minutes) and I am only getting 12V at the battery.

It looks as if my car just ate a good alternator. I have also heard of alternators going bad when you make them charge dead batteries (and mine was pretty close to that), but would that explain the drop below 14V a few minutes after installation? I'm afraid that there is another problem that I'm not seeing here, and don't want to go through the effort/cost of installing another alternator until I can be sure that this is the problem.

I checked the belt tension and all fuses, and that doesn't seem to be the problem.

Any ideas?

[A18A]

try installing a new wire that goes from the alternator to the battery/fuse box. or maybe you just had a bit of bad luck and bought a alternator that was on its way out. they (usually the brushes, not the alternators) quite often fail in these cars after a good 20 years or so