00WhiteEKy

OK. Here is the problem. My brother dropped a new motor into our 89 prelude si. WHen i got back from school i went to work on it. The alt. was bad from the new motor, so i sent it in to get rebuilt. New brushed and a regulator was put in. I put the alt back in, and no luck. Nothing happened. No 14 volt at the battery, no charge. i took it to auto zone and they couldn't get any reading on the alt. SO im thinking its bad. I took it back there i got it rebuilt, and the old guy there put it on his tester and then it reads 14V. ????? The old guy ran 12 volts to a wire in the plug, and the post said it was charging? weird. so i checked my wiring in my car, and everything was working fine. the right wire was sending 12v to the plug, but of the post it did not read 14v at all while the car was running. All the fuses are good. Im wondering what the other 3 wires on the plug are for on my car. 2 are like decoys in the plug, and the other i think might be for the check engine light. I don't know whats wrong. Does it matter which way the alt. spins? becasue some testers spin the alt one way, and the car spins it the other way. But auto zone and the old guy's machines both spin the alt. the same direction. What else could be wrong??? Please, i need any help i can get. this is the last problem with the car and then it will have a complete rebuilt motor and ready for another 200,000 miles. HELP!!!!!!!!!!! EDIT: This wouldn't be a battery problem, would it? If it was the bettery, the alt. would still read 14v off the post, right? This is bugging me.

kablamo

did you get the battery charged up before putting in the rebuilt alternator?

it was kind of hard to read your post, but it doesn't sound like the guy who rebuilt it did an actual bench test. if that's the case, i wouldn't be surprised if he is just bullshitting you, and the alternator is actually still bad. what's important isn't how many volts the alternator is putting out, it's how many amps. Any amount of amps the alternator puts out is going to be around 13.2 volts plus or minus 0.6Volts, that is spec, but what is really important is the amp number. To get that, you have to test it under load, using a benchtester. my guess is your alternator is not putting out nearly as many amps as it should. 3rd gen prelude alternators should put out up to 65amps (although you won't get that kind of reading on a bench tester).

rebuilding an alternator doesn't guarantee that it will work, it just changes parts that likely break - and that's if it's done right. you might have to cough up the money for a rebuilt unit, which at least will have a guarantee (in case anythign weird happens).

00WhiteEKy

ok, thanx. I think i might just order a new alternator and see if thats works. I really think the old guy who rebuilt my alt. didn't fix everything. I know auto zone has a life time warrenty on a alt. there. I will probably do that. If the new one still doesn't work, then i will be confused. What are the 4 wires on the plug really for anyway? I just want to make sure those are all right.

kablamo

i'm not entirely sure what they are for, but any alternator will have a few extra wires. they basically hook up to the engine management system (ECU) and give it some info. if you bench test the thing, you're supposed to hook them up on the machine, otherwise you won't get certain readings.

i think you'll be better off with a new alternator (well a remanufactured one, that's all they sell), and make sure that the battery is charged when you install it, or you're going to put a high stress on the alternator until it charges the battery AND runs the car.

if you dont have a charger, most parts stores will do it for cheap, hell some even do it for free (especially if you are buying an alternator).

edit: alternators are a fairly common thing to go on 88-91 ludes, so it's entirely possible that is the problem.

00WhiteEKy

I have a quick question. The old guy tested m alternator with just his volt meter, but it was a test to test the alternator under load. I reading up on alternators becasue i want to learn a lot before i go back to the old guy to tell him whats wrong. I found out that if a winding is bad, it will still put out voltage, but only under load will you actually see the problem. what are some other simple tests i can do on the alternator to find the problem? I do have a couple fancy testers, but not sure how to test an alternator. BTW, i do have a battery charger, so i will have a charged battery when i put the alternator on.

kablamo

Well testing the alternator under load implies that it is turning at least as fast as it would if the car were idling, when it has to power basic accessories.

you need a benchtester to do that (something autozone should have), but the guy who fixed it may not (it's a fairly expensive piece of equipement). a decent benchtester will give you readings for the voltage and output of the alternator, and other readings as well, which just have to be within spec.

with a voltmeter, all you can do is make sure everything is put together right, and there are no short circuits or funky things going on. it will by no means test that it can actually create power and specifically how much of it.

if you go back to autozone, ask if they will let you see the machine testing the alternator, i used to work in a parts store and we'd show customers sometimes (especially if they didnt believe us but sometimes cause they wanted to see the readings).

if and when you buy an alternator, they should test it for you on their benchtester BEFORE selling it to you, that way you can make sure that it works. And in the off chance that it doesn't, and you take it back and they will test it again and find that it doesn't work, then you will know something in the car is causing the alternator to go bad (unlikely but it happens). they will still have to give you a new one though (warranty hehe).

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 92hatchy &raquo;</TD></TR><TR><TD CLASS="quote"> I found out that if a winding is bad, it will still put out voltage, but only under load will you actually see the problem. .</TD></TR></TABLE>

This is exactly why you need a benchtester to do a proper test - a lot of problems only show up when the alternator is spinning at speed and required to produce power. Just spinning it alone is not enough, it has to be "told" to produce power (something one of the wires in the 4 you were mentionning does).

00WhiteEKy

ok, now im really messed up. A different parts store said it was my battery. I had a good battery lying around, so i put that one in, but the alt. still does not charge. BUT!!!!!!!! I did make some new interesting discoveries. but something with the regulator is bad, but its a brand new regulator. if i run a wire straight from the battery to the plug on the alternator (the field voltage) it will then charge, and everything is all happy. I checked the wire in the plug, but the wire in the plug is also giving out 12 volts- so that is right. hmmmmmmm???????? there are 3 other wires along with the field voltage. all are white, one has a red stripe, one has a red stripe, and one has a kinda greenish stripe. (i have a picture if anyone wants to see) I think maybe one of these wires are telling the alternator to not charge. does this make sence to anyone??? One other thing i tried. I ran a jumper wire from the plug (the field voltage wire-which is the black with yellow stripe) to where the alterternator needs the fields voltage. (hope you follow this) and then it charges, whoo hoo, but if i shut the car off, and re-start the car, it will not charge, unless i take the wire off and attach it again. which doesn't make send becasue im running a jumper wire from the exact wire in the plug that the alternator needs. something is really really fishy here. Bad regulator? wrong regulator? im thinking one of these 2 is the problem. But at least i can drive it with the jumper wire, just when i go to start it, i have to go under the hood and take off the wire, and re attach it again to make it charge. But im not going to drive it untill i get this problem fixed. My head is about to explode becasue i am running out of ideas to try on here. ANY HELP IS VERY MUCHLY NEEDED!!!

00WhiteEKy

bump for the late night crew. i still don't know what the other 3 wires in the alternator do. and im not sure if my alternator's regulater is the wrong one or not. not sure my problem yet.

kablamo

yeah sounds like it could be the regulator.

i'd still recommend that you change the whole alternator though. the guy that did the "rebuild" seems to have screwed it up big, and if this is the original alternator (which it may very well be), something else could go on it again - so if you can get one with a long warranty it might work out best. i guess it depends how long you are going to keep the car/how much it costs/etc...

what you are saying about he one wire saying to the alternator not to charge could make sense, although i dont know where that wire leads back to (my guess some circuit connected to the ECU) but i wouldnt' know how to diagnose it - the shop manual probably would say that though. do you have access to the 3rd gen lude shop manual? there is one scanned on the internet and available (sorry i dont have a link). i'd definitely check that first.

mcphebb

Ok I know this is a very old thread... but I have a 1988 Prelude SI 2.0 5 speed and it is having a very similar NO-CHARGE problem.


The alternator checked good. I went ahead and replaced it with a rebuilt alternator from Autozone. Still not charging.

I replaced the battery with a brand new battery. Still not charging.

Replaced the alternator AGAIN with another rebuilt unit (different supplier). Still not charging.


I checked the fuses:

The 10 amp fuse under the dash (shows for alternator & fuel pump) is good AND all the fuses under the hood (in the engine compartment fuse box) are GOOD.



I checked the wiring at the alternator plug:

The GREEN alternator plug has 4 wires.

Here are some readings from multi-meter tests of the 4 wires:

1) White/Green - ign OFF: 12v, ign ON: 12v, engine running: 12v

2) White/Red - ign OFF: 0.5v, ign ON: 1.5v, engine running: 1.5v

3) Black/Yellow - ign OFF: 0v, ign ON: ~12v, engine running: ~12v

4) White/Blue - ign OFF: 0v, ign ON: 0v, engine running: ~12v


I created a small wiring harness extension for the GREEN alternator plug (just 4 wires with terminal connectors), to be able to get the readings above, with a multi-meter without damaging/poking the wires.


When the battery is freshly charged and connected freshly from sitting overnight, both alternators will charge for about a minute (at 13.45v), before slowly going down to not charging state.

It then settles in to low 12.xx v, where it starts pulling the battery down.



I have tried running the car with only the big terminal wire connected (the one that runs to the battery/fuse box) AND the Black/Yellow wire on the GREEN alternator plug.

It did NOT charge.

After reading your post.. tomorrow, I will try starting the car first, then unplug and re-plug the Black/Yellow wire in the GREEN alternator plug, to see if it starts charging.


At this point, I am starting to wonder if the computer (ECM), might be bad.


Before replacing the ECM, thought I would post this, to see if anyone could help or provide any suggestions.



Thanks!

aisyhaoaysbaaio

Ever manage to fix your problem?