alternater - replaced everything
 

i dont understand!!! car will not charge, has a new battery, tired 3 new 97amp alternaters. everything is hooked up. i tested the intput wire, it has 12.10 and output is the same, i am testing from the alternater itself. Inside the car say it charging at 11.6. what esle could the problem be?

The wires thermselves could be bad, are they corroded at all?

output wire isnt in the best shape. but im testing from the alternator itself

Well if you're checking at the alternator then all you know is that it works. You want to know what's getting to the battery. Check the voltage drop between the battery and the alternator. Put the positive lead of your meter on the output terminal of the alternator and the negative lead on the positive post of the battery. If you are reading more than a volt or o then the wire has too much resistance, you need to get a new one. If that checks out okay then check the voltage drop between the negative battery post and an engine ground. That should be less than half a volt, or maybe even .2 volts.

its like .5 or .8 of a volt

clean the ground wire at all ends of connection

you realy think thats the problem?? the grounds look ok. still doesnt understand y the alternator not puting anything out?

Don't forget about the "other" wire. The one that goes to the dash. Some models it goes to the ALT light others it goes to a resistor in the dash. It supplies power to the regulator to turn it on. I use it on mine to "sleep" the alternator at WOT to free up horsepower.

the exsiter wire it should have power when the ignition is turned on.


Good bloody show mate

both the power wires have power. i think it more of something like something is grounding out or something draining the battery.

when you say both the power wires have power what do you mean. we are talking about the wire in the plug at the back of the altenator,

the wire that goes from the pos battery cable to the terminal on the altenator should be replaced since I read the post over again and you mentioned it is not in the best condition.

It is a good Idea to clean the grounds in your car every once in a while- preventative maintenance

When you turn the key to "On" with the engine NOT running, does the "Choke" light in the dash come on?

If not, replace the "Choke" bulb; see if it comes on, as described above. Then start it up and see if the alt works.

The light that says "Choke" is really the "Alt" warning light. The alt receives its "excitation" current through that bulb. If it's burnt out, the alt will never "know" that the key is on, and therefore will not charge.

its not carb, its tpi, so there is not choke light. the alternator light does work. when i hook up the test light from the engine ground to the negative post on the battery it lights up real bright. the mutimeter show .5 or .8 volts. so i think something is draning the battery? yea both the plug and the output wire has power.

explain a little better what you are doing when you get the test light to go off.

where do you hook up the engine ground. are you talking about the place where the ground cable connects to the engine.

I would check the routing of the wire that goes to the altenator from the positive battery cable.

yea, im connecting the negative battery cable to the negative post and it lights up. so doenst that mean somehing is draining the battery real bad

yes it does. pull your car into a dark garage. turn the car ign on but not running and more the harness around you should see a spark

but does that make sense, that im not see 14volts at the alternater

That's right. Stay focused. If a light is left on somewhere and you run the engine you should still have 14+ volts at the back of the alternator. Don't forget the belts have to be tight and the pulleys not worn for the alt to charge. It happens. If you put 3 alternators on, your auto store (if it is any good) should have tested at least one that you brought back.
You are sure you have positive voltage on ALL of the wires at the alternator when the engine is running? (not the ground wire of course)

had the alternator tested, its good. r u saying no matter wat the drain is, it should still be 14volts at the alternater? this is crazy, cant believe no one had has this problem before.

dude you can take it to the shop or start checking the entire charging circut.

Yes that's right. It would have to be more than a 30 amp load and it would be easy to spot because it would be GLOWING or SMOKING Check the voltage on the wires connected to the alternator with the engine running. Everything that is not a ground at the alternator should have atleast battery voltage or battery voltage minus 2 volts. Don't forget to check the pullies and the belts.

I would also say that a .5 to .8 volt drop on the battery ground is a little high. Make sure those grounds are clean and the wires are not corroded.

There is a light that should come on. If it doesn't come on, your alt will not charge.

I wouldn't be so sure that it isn't labelled "Choke", just because your particular intake system doesn't have a choke. But regardless of the label on the little sheet of red plastic covering the bulb cavity in the dash:

Does the light in question come on?

If it doesn't, your alt will never charge; and you can change parts and have them checked and post on the Net from now till doomsday, and it will do no good.

Check the bulb.

I have to ask about this bulb. In all the diagrams I've seen for charging systems the warning bulb for the alternator was on a parallel circuit to the rest of the charging system. So it was unrelated, it couldn't cause a no charge situation. Is the design different on 3rd gens?

No it is not a "parallel circuit". It is a SERIES circuit; specifically, the bulb is in series with the 12V feed from the ignition switch to the armature and regulator, via the diode trio. Which is why the alt won't start if the bulb isn't there: there is no 12V produced by the alt at the diode trio until the alt starts charging, which will not happen unless either the bulb supplies some current, or the alt just happens to have enough permanent magnetism in its iron, to be able to start up (which they usually don't).

Trust me, I've seen this happen countless times over many decades now.

Of course, if you choose not to believe me and try this simple stupid cheeep thing, it's your car that's not working. ;) Mine works just fine. Bulb and all.

The bulb that says "Volts Indicator" in that schematic (yes, I have a factory service manual too ;), mighty handy if you ask me!!) is actually the "Choke" light.

How long does it take the battery to go dead? A few hours, or a day or more?

I know one thing for sure that will drain the battery in less than a day, whether key is in ignition at all or not - fuel pump. My Oil Pressure Sending Unit went bad on my car (TBI), and allowed juice constantly to the fuel pump, even when key off and in my pocket. But the fuel pump was quiet, and I couldn't hear it running without laying my ear on the trunk hump in the middle of the night when all was quiet. That's only idea I have - it's something to check anyway - if the pump runs without key on, then try replacing OPSU.

im like almost sure the bulb isnt burnt out but imma check to make sure again. its a lil harder 4 me, i have the dakota digal gaugles. the battery will go dead after 2weeks (i think), not to sure just bought the car and put a new battery in. afraid to leave the battery hooked up, lol. wat, if the ignition switch was bad, would that cause a no charge? ok ill have to check tommrow cause it raining right now. thanks 4 all this great info, were gettin somewhere. lol

The TPI varies slightly in that it has one lamp, while the carbed versions seem to have two:

http://72.19.213.157/files/ChokeLight.jpg

one more question. i heard if the bulb was burnt out, there would be no resistances in the input wire. true or not, if so how much should i look for?

My 87 IROC-same prob
 

Hey, this may sound stupid, but I had EXACTLY the same problem on my 87. Swapped out wires, alternators, traced grounds, etc. Couldnt get it to charge. Here is what I found............my FAN fuse was blown! Why Chevy ran the charging circuit thru the fan fuse I dont understand. But I replaced the fuse, and everything started working fine. I dont know if your wiring is the same as mine, but figured I would pass on what I found on mine.

ok guys, you ready to hear wat the problem was. when i bought the car it wasnt charging, so i got a new alternator and it still wasnt charging. it turns out the parts store keep give me the wrong alternator, the problem was the lil output nut keep touching the valve cover and grounding out. destorying the alternater.

So you got a different alternator then I assume, where the bolt wouldn't touch the valve cover? If so - then I have some questions:

Is the alternator on the driver side?
Serpentine setup?
What part number for the new alternator that DOESN"T touch the valve cover?

I ask because - My alternator has a post that wants to touch - I knocked a dent in my valve cover to solve the issue - but I'd like a nice new set of chrome covers, and I'd hate to bang a dent into them.

nah, its on the passenderside. u need a cs-130 alternatoer