charging problem has me stumped

[cruznthastrip]

I'm new to these imports, I've always worked on older(before 80's)RWD GM cars. But I found this 86 accord for $400 on a weekend trip after my daily driver broke down. It has 260,000 miles on it's 4cylinder/5speed, but it has tons of reciepts and lifetime warranties on it.
After about 3 days of driving it, the charge light came on. I kept driving it daily for about another 3 days and it died. The battery was dead and it seemed like the altenator wasn't charging it. I know the light was warning me about that. So I figured the altenator was bad, bought a new one and put it in, a very big pain. I brought the old one in it and it was tested to be good. But my charge light went out so I thought everything was good, but then 3 days later it died again(with no warning light)I went to the manual avalible from this part of the forum and tested all of the wiring with the new altenator in it. Al the wiring checked good right at the alt connection. One was always hot and 2 went hot(12v) only with the key only in the on position. And the bigger battery wire from the alt was also ok, but it was not putting out volts when running from the post on the alt. The warning light also tested to be ok and all points to the voltage regulator.
It seemed odd that a new alt/volt regulator would be bad, but that is the only thing that the tests point to. When I do the "field test" with the screwdriver in the back, it jumps up to putting out 17-19 volts.
Any ideas on what maybe wrong? It is stumping me and my other mechanic friends. I'll be calling a Honda Dealership in the morning, but I figure they're going to want a lot for something that I have already checked. Thanks and sorry for such a long post, Mike

[accord upset]

you checked the battery maybe its bad, just old or internal short? and when it gets low the alternator may not keep up with running the car/accerories and charge the battery. check the voltage with it running with no accories? make shure the lil round plug that goes into the back of the alt is staying connected. do the old start it and pull a battery cable trick while it running and see if it dies? if so alternator is not charging right if not u got other problems namely battery or wireing. i had a truck that i was working on, one of the relays for the alarm would stick and it would run the batterydown in like 2 days.

[cruznthastrip]

The batterys new(2years olds) and I tried another out of another one of my cars. The volts definately drop with accessories on, but it seems to be pulling all off of the battery. It does die when I pull the cable off and when I do the field test the alt will put out volts, but only then and then it's too much because it bypasses the voltage regualtor I'm told. I just can't believe I'd have a bad voltage regulator on a new alt, but that seems to be what the tests point to. I'll look for anything grounding out elsewhere tomarrow. With the voltmeter, I'd see it drop about .01volts every 15 seconds with the tester on it.

[accord upset]

well sounds like the alt to me,,please tell me u didnt go to auto zone to get it.
i dono if what i said helped any but good luck man. im out for tonight

[Tailfin]

There is a more direct way to test the alternator and battery, but this does not rule out shorts and such...but it's easy to do first. With the car running, put the voltmeter on the battery terminals. You should be getting low 13 to low 14 volts or so. If you are, and it's consistent, not crapping out at moments, then the alternator should be fine.

With the car off, do the same, and the battery should be giving you around 12.

2 years is not new for some batteries...it's possible for the battery to be bad, especially if it's a cheapo or if it had stress put on it, like being drained and charged on multiple occassions (or the aforementioned electrical problems)...but if the battery's bad, a good alternator won't matter, because it won't hold the charge. You can test this by running the car, then stop it... Test the voltage right then... If it's under 11, then you either have a really bad battery or an electrical drain somewhere. Anyhoo, then pull the cables off the battery. That way, you can diagnose if it's the battery or the electrical drain. Let it sit overnight, then check the voltage again. If it's down, then the battery is not holding the charge. If not, then it's probably something grounding that shouldn't...which is more of a pain hehe... All I can say from there is check any diodes or other stupid things that have already been mentioned...

Just for kicks, check out the belt for the alternator and make sure it's got proper tension and isn't slipping or oily or something.

[shepherd79]

test your battery, and it does sound like you bought bad alternator. It happens sometimes. take it back and exchange it. it should be under warranty.
your alternator should put out between 13.5 and 14.4V. anything above or below is not good.

[Blkblurr]

ARe you sure the wiire from your alt to the battery is good? Could be corroded enough that it only passes low amounts of current. It may test good under no load but when you are trying to charge the battery or run the accessories, it may not be albe to supply enough current to be able to keep the voltage up to 13.6

[cruznthastrip]

I found out what the problem is/was. I thought the altenator was the problem, so I replaced it. After that, I looked around the engine compartment and found a bad butt connector that someone had spliced for one of the smaller alt wires(white/green wire) So I fixed that, but still had charging problems. All the tests pointed to a bad voltage regulator...on a new altenator. So I bit the bullet, and swapped the alt again back to the old one that tested to be good. Then, I brought my new one that was just in the car back to the store, and found out it was bad. Everythings good now.

So the morale of the story is, check your wires first, before replacing the altenator. And, if you have one of those hard to install altenators, test the new one at the store when you buy it, just to be sure.

Thanks you to everyone for the warm welcome and all the technical insight.