Why Won't A Brand New Alternator Not Charge A Battery?


7 Answers

David C Profile
David C answered
Pull the pos strap off of the battery when the car is running, if it dies and you know that the alternator is good you could have a short. That could be what is killing your batteries.
Is your car killing batteries overnight? Could have a short somewhere else and that short just put more strain on your old alternator. Oh.. And I've been working on cars for 5 years and although I have very extensive experience with all sorts of cars I still make mistakes.  Ever see the issue of Hot Rod Magazine where they put an engine together and fire it up just to have it explode? They were mystified by what had made it do it until they took the engine apart and found out that they had left a ratchet inside of one of the cylinders! Everyone makes mistakes so don't assume that you did it perfectly.. And don't chew people out who are making suggestions.. You asked for the help!
thanked the writer.
Anonymous commented
Thank you for the advice. I have checked and taken into consideration what everyone has suggested before I got on to this site. So everything that has been suggested here has already been gone thru. That is what makes this so frustrating. What I really need is a set of full schematic wiring diagrams. I can't find anything wrong with the exposed wiring. I now have to go through the unexposed wiring. I have to take the dash out and trace every wire there, including the steering collum. Possibly having to replace the harness and the whole wiring setup.
David C
David C commented
Shoot well... I guess if it is so much trouble and you've spent a lot of time on this problem maybe you should buy a repair manual for the vehicle that's got a good wiring diagram in it. I hate having to buy manuals for different vehicles cause I've got a big stack of them in the garage from different vehicles that I've worked on in the past. I moved to all data a while ago since it has a pretty thorough system. Good luck tracing that wiring, I know it's such a pain to do.
Anonymous commented
great answer, thisismyac, and patient too .
Rena Chisholm Profile
Rena Chisholm answered
We would say that if your alternator went bad, your car was running solely off the battery, which could ruin the battery.
Have the battery load tested.
Would be our bet that you need a new battery. Have seen this many times.
 Assuming that your new alternator is working.
♀  &  ♂
thanked the writer.
Anonymous commented
it has killed two brand new batteries. Checked all connections, had both batteries tested by two different places. alternator was tested both in the car and out of the car. tests showed that the alternator is not sending a charge to the battery while in the car, but tests perfectly fine out of the car. the problem is in the wiring.
What else do you guys got?
Rena Chisholm
Rena Chisholm commented
It would have been nice if you would have put ALL this information in your question. The MAKE, MODEL AND YEAR of your Vehicle Would Also Have Been Helpful. Maybe we wouldn't have gotten such a bad rating from you on our answer.
If you re-read your question and look at it from (the readers point of view), you might realize that we really didn't have much to go on.
Maybe someone else on the site will be better suited to answer your question. Just leave it open and maybe, somebody will try to help you out with it.
Just my opinion, but I don't believe most blurters like to get bad ratings when they are genuinely trying to help someone out. Have a nice day.
John Profile
John answered
I would say it is the installers fault and that the alternator is probably working fine, but the alternator is either hooked up wrong or has a broke wiring harness or the belt is under driven or  this is the wrong alternator for your vehicle. or the best answer is you have a short somewhere causing the charge from the alternator to not reach the battery. In other words the pathway is broken. There can only be a few answers to this question. Something is broken/loose(wiring) /installed wrong/or the wrong part. Try the z net from autozone. It will give step by step instructions. You need to include further information of the vehicle(year/make/model/size engine/ if you want specific information.
thanked the writer.
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Rena Chisholm
Rena Chisholm commented
Okay, after reading, the rest of the info, which you (finally) gave us, and, even though you called us stupid, I have decided to go ahead and tell you what the problem with your vehicle is, anyway.
It can only be one of two things and I am assuming that with your 14 years of experience, you should have no problem figuring them out.
It's either the S or the A. H U W. Being a man of such extensive knowledge, I'm sure that you will immediately know what those letters stand for, mr. nasty guy.
So, as you can see, I can be a nice person.
As always, Have a nice day.
John commented
also here is a expert on alternator problems from expert village below the video is the testing procedure for the wiring harness and fuse. http://www.expertvillage.com/video/13359_alternator-diagnosis.htm
Michael Vore
Michael Vore commented
can we get one of those speak -n-see diagrams for him... or mebbe one like they have on the airplanes for what to do when your gonna crash?
Anonymous Profile
Anonymous answered
Resistance in the wiring due to corrosion or poor ground. Sometimes theres a regulator that controls the voltage and amps within the alternator that is defective.
larry cook Profile
larry cook answered
Have you had the battery checked to see if it didnt go bad when the alternator did or maybe the alternator was bad from the start an now its not charging .one way to see is to start car with nothing on in the car an remove hot lead from battery car should stay running if it do turn head lights on car should die
Michael Vore Profile
Michael Vore answered
Grr ... If you been working on your own cars for 14 yrs then why don't you know? Instead of bashing people who are just trying to help a person who isn't smart enough to take the darn wires off and put in new ones cause there's a short .... Go back to your pile of junk and stop hating.
Anonymous Profile
Anonymous answered
The alternator is not designed to charge a battery

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