Alternator works but it won't charge the battery..

Posted by randizzle420, Mar 8, 2010
Newbie Forum - Beginner DSM modification questions and discussions. Common, repetitive, and general discussions will get dumped here from other tech forums. Unless you're a Probationary member you shouldn't post threads here.

  1. randizzle420

    randizzle420 Proven Member

    Joined:
    Sep 20, 2009
    Posts:
    89
    Likes Received:
    0
    San Diego, California
    I just bought a new battery, and it kept going dead when I was driving it. I was pretty positive it was the alternator because I tested the battery when the car was on, and it was only 12 volts. I took the alternator off, took it to pep boys, they tested it, and the alternator is fine, was putting out 14. something volts. Any ideas what the problem might be?
    #1
  2. etay89

    etay89 Proven Member

    Joined:
    Dec 27, 2009
    Posts:
    398
    Likes Received:
    1
    Monroeville, Pennsylvania
    i was having a similar problem, except i have a new alternator AND battery. i never attempted to fix the problem, but my guess is probably wiring somewhere.

    my car would have trouble turning over or whatever else in between, then i hooked up an air fuel controller and have it monitor my volts.

    when you run electronics in the car (cigarette lighter, radio, turn signal, headlights, etc.) obviously it uses the battery power...but overdrawing power things (an amp, 55w silverstar headlights, holding on the brake at a long light, etc) drains power faster, dims light, and hurts performance

    my advice to u if you are concerned is buy a cheap voltmeter, and monitor it yourself. wanna spend a bit more? get a voltage gauge or an air fuel controller.

    *edit* also, try just driving it around constantly for about a half hour at high speeds (get on the highway and then turn around) to see if the alternator charges the battery. at off, the battery should be between 12.8-14.8. if it doesn't then you may need a new alternator.
    #2
  3. randizzle420

    randizzle420 Proven Member

    Joined:
    Sep 20, 2009
    Posts:
    89
    Likes Received:
    0
    San Diego, California
    The battery is new and the alternator was just tested at pep boys and the alternator works. I did drive it on the highway and the battery died on me and I had to get my car towed.
    #3
  4. tallywacker

    tallywacker Proven Member

    DSM Profiles:
    1
    Joined:
    Dec 2, 2002
    Posts:
    347
    Likes Received:
    1
    Mercersburg, Pennsylvania
    I can't wait for mine to die again so I can do the Saturn alternator swap and not have to worry about it for a long time.
    #4
  5. etay89

    etay89 Proven Member

    Joined:
    Dec 27, 2009
    Posts:
    398
    Likes Received:
    1
    Monroeville, Pennsylvania
    something in your car is drawing alot of power to cause it to die. now if its dying while it's running but stopped...thats one thing. if it's dying while its moving, that's another. you probably have a short somewhere. check all alternator wiring, make sure the battery terminals are clean and that the negative is properly grounded.
    #5
  6. randizzle420

    randizzle420 Proven Member

    Joined:
    Sep 20, 2009
    Posts:
    89
    Likes Received:
    0
    San Diego, California
    well I put a new ground in for the battery, cleaned the posts and everything. I'm still having the same problem with the battery not being charged by the alternator. The battery light just stays on in the car. Also, if I turn my headlights on then turn them to the off position the headlights stay on. Only way to get the headlights to turn off is to unplug the battery.
    #6
  7. etay89

    etay89 Proven Member

    Joined:
    Dec 27, 2009
    Posts:
    398
    Likes Received:
    1
    Monroeville, Pennsylvania
    then you have some type of crazy wiring problem. i'd get it checked out
    #7
  8. 1995gsx20g

    1995gsx20g Proven Member

    Joined:
    Mar 4, 2008
    Posts:
    667
    Likes Received:
    5
    Huntington stat, New_York
    to me it sounds like you have a problem with your voltage regulator within the alternator.
    - the issue with your headlights could be when your alternator is putting out around 16v-18v the relays in your car like your headlight relays act very funny and do crazy things.

    - i got a "rebuilt" alternator from a parts store and the voltage regulator was only charging 12.3v at idle but above that at around 2k and up it would act normal aka why pepboys thinks its good. but if you let your car idle for a few seconds it will drain your battery. so it will not start back up once you shut it off but if you hold the rpm at 2k for a few mins and shut it off at 2k then go to restart it, it will start up.

    - like stated above your car shutting off WHILE driving sounds like a short or a poor ground that can be more than just at the battery. when it shuts off do you lose all power to accessories also?
    #8
  9. 91Bomb

    91Bomb Proven Member

    Joined:
    Jul 15, 2003
    Posts:
    618
    Likes Received:
    3
    US, New_Jersey
    Aftermartet alts are known to have voltage regulators that don't work right with our cars or somethinhg to that effect. I put 3 pep-boys alts in my car in 2 mth period and have read many times about other dsm'ers doing the same thing with atouzone alts, advance, etc. Best bet is to get an oem alt and pm me if you want a good used oem mitsu alt cheap because I'm parting out one of my dsm's.
    #9
  10. randizzle420

    randizzle420 Proven Member

    Joined:
    Sep 20, 2009
    Posts:
    89
    Likes Received:
    0
    San Diego, California
    I found the culprit! It was a bad alternator relay. I replaced it and now everything runs good.
    #10
  11. spydreclips6

    spydreclips6 Proven Member

    Joined:
    Dec 8, 2005
    Posts:
    73
    Likes Received:
    0
    French Lick, Indiana
    I know you took your alternator off and to pep boys to test it, but you should test it with it still in the car to figure out what your problem is. Use your multimeter (if you don't have one get one). Turn it to dc volts put your leads on your battery (with the car running), if your alternator is charging it should read from 13.5V-14.5V(thats a good charge). If your not getting a reading from there you can check your output from your alternator. Make sure you ground your multimeter, and put the power side to the stud that is coming out from the alternator(should be nut holding your wires that go to your battery). If your getting 13.5-14.5V there then the connection between the alternator, and battery is bad. Hope that helps! :thumb:
    #11
  12. 9!'clipseDOHC

    9!'clipseDOHC Moderator

    DSM Profiles:
    1
    Joined:
    Aug 24, 2003
    Posts:
    3,447
    Likes Received:
    114
    El Paso, Texas
    I was just reading through your post and thinking, sounds just like a blown ALT fuse. Glad you figured it out. Wish I'd seen your post earlier, I would have pointed you in the right direction. Good luck!

    Also, don't forget to mark this thread as solved/resolved.
    #12
  13. 4g63t

    4g63t Proven Member

    DSM Profiles:
    1
    Joined:
    Aug 14, 2005
    Posts:
    775
    Likes Received:
    4
    North Iowa, Iowa
    So my alt spikes up to 17v to 18v for a few min at a time then it will run the normal 14.v. Would this be the alt relay too. It is a new alternator. Or would it be the voltage regulater is bad in my new alternater.
    #13
  14. Jarnutt

    Jarnutt Proven Member

    DSM Profiles:
    1
    Joined:
    Sep 21, 2009
    Posts:
    81
    Likes Received:
    0
    Peoria, Arizona
    That's a bad regulator hands down. Sounds like its not regulating anything anymore and its sending full field voltage to it causing it to max out on the charge. Anything over 14.8 is abnormal usually, anything over 16 can start to eff up electronics, you'll be lucky if your ECU/TCU survive too many of those spikes
    #14
  15. 4g63t

    4g63t Proven Member

    DSM Profiles:
    1
    Joined:
    Aug 14, 2005
    Posts:
    775
    Likes Received:
    4
    North Iowa, Iowa
    Damn, o'well im going to take it out next time it does it. I just baught it so ill just return it for a diff one. (My power windows whoop ass at 18v LOL)
    #15
  16. Jarnutt

    Jarnutt Proven Member

    DSM Profiles:
    1
    Joined:
    Sep 21, 2009
    Posts:
    81
    Likes Received:
    0
    Peoria, Arizona
    ROFL Lots of stuff woops ass at 18v, like a cordless drill LOL.
    Id get it taken out and swapped, voltage spikes are NEVER good.
    #16
  17. Sandman817

    Sandman817 Proven Member

    DSM Profiles:
    1
    Joined:
    Mar 2, 2010
    Posts:
    285
    Likes Received:
    2
    Lower Fairfield, Connecticut
    Just for future reference, a quick easy way to check if an alternator's dioeds are bad is to get a Multimeter, put it on AC VOLTAGE. put a lead on each terminal while the car is running. If you get anything more than .5volts one or more of your diodes are going bad.

    Diodes convert AC voltage to DC voltage which can be stored in your battery.
    #17
  18. Krueger84

    Krueger84 Probationary Member

    Joined:
    Jul 24, 2010
    Posts:
    8
    Likes Received:
    0
    Destin, Florida
    I have the same exact problem on my 1995 Tsi but I can't find where the alternator relay is on my car, can you please point me in the right direction. My car has been down for about 4 months now with this problem and I've replaced the alternator, battery and ecu. I would appreciate any help. Thanks in advance.
    #18
  19. NOTORIO3030

    NOTORIO3030 Probationary Member

    DSM Profiles:
    1
    Joined:
    Nov 11, 2012
    Posts:
    10
    Likes Received:
    0
    Manhattan, Kansas
    Yeah my 95 tsi is not holding the charge at night when i turn the lights on so i cant race nobody at night because it starts missfiring at 20 psi
    #19
  20. 93 gsx skidz

    93 gsx skidz Proven Member

    Joined:
    Sep 15, 2012
    Posts:
    43
    Likes Received:
    0
    masontown, Pennsylvania
    I'm having kind of a similar problem. But my accessories and lights don't work. The car runs and starts up fine but the battery will die after running it for a while. I can't even roll up my windows. What do u think it is
    #20
  21. miguelmcv

    miguelmcv Proven Member

    DSM Profiles:
    1
    Joined:
    May 3, 2009
    Posts:
    1,833
    Likes Received:
    10
    Fresno, California
    Check the voltage on your batter and alternator, You might have just a bad alternator.

    Check the alternator fuse as well.
    #21
  22. 97_GST_DSM

    97_GST_DSM Probationary Member

    Joined:
    May 23, 2013
    Posts:
    1
    Likes Received:
    0
    Central City, Iowa
    I was having a similar issue, turns out that the bolt on the alternator rattled off and was causing it to not start after i turned it off. in which i had to jump it every time i started it. hope this helps someone
    #22
  23. bduran1220

    bduran1220 Proven Member

    DSM Profiles:
    1
    Joined:
    Nov 26, 2011
    Posts:
    153
    Likes Received:
    0
    Las Vegas, Nevada
    Yea I have the same problem too, it hella annoying. Having the the Batt and alt. Monitored while driving its fine but at idle with headlights radio radar ect ext. it bites.....even with a new OEM 70 AMP ALT. what bites even more still acts the same way with the 90 amp alt.
    #23
  24. Meeegaaa_TRON

    Meeegaaa_TRON Probationary Member

    Joined:
    Oct 5, 2012
    Posts:
    1
    Likes Received:
    0
    Delavan, Wisconsin
    so can anyone describe were the alternator relay is at? and where you can buy one from?
    #24

Share This Page