1. Join the Community!

    DSMtuners is a massive archive of DSM information - but more importantly, it's a COMMUNITY! Join in and participate with other DSMers, and invite all of your DSM friends to make this place their home. Chat with others, create a build thread, post questions and answers. Get involved! Logging in will also remove many of the advertisements, along with this notice. ;)

2G Is my alternator bad?

Posted by bo0st, Aug 18, 2020

Please Support Southbay Fuel Injectors
Please Support Feal Suspension
  1. bo0st

    bo0st Proven Member

    830
    20
    Joined Jan 26, 2010
    Phoenix, Arizona
    Sometimes my AEM volt gauge will display 7v and at other times it’s displaying 12-13.

    FYI: I’m unsure if this alternator was ever replaced. The battery itself is a brand new red top optima which is testing well

    also if it helps I could upload a log from link
     

    2K  1

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  2. SasaniFab

    SasaniFab Freelancer

    2,467
    764
    Joined Dec 1, 2013
    danbury, Connecticut
    Haved you tested the battery voltage with a volt meter when the cars idling?Id start there
     

    Street Build 4K  20

    1992 Eagle Talon TSi
    645 whp · 498 lb/ft · 1G DSM
    Loading...
  3. Dericsh

    Dericsh Supporting Member

    550
    43
    Joined Nov 25, 2002
    Pearl River, Louisiana
    If that’s your only symptom I’d be looking at the connections for the gauge. And like mentioned above compare the readings with a volt meter
     

    Street Build 388  2

    1991 Mitsubishi Eclipse GST
    fwd · manual · 1G DSM
    Loading...
  4. Sniffbooger

    Sniffbooger Proven Member

    218
    72
    Joined Apr 12, 2020
    Torrance, California
    When idling, the voltage tested at the battery should be approx 14.3 volts on a 2g. This shows the alternator is working properly.
     

    Street Build 350  8

    1998 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  5. jpmxrider489

    jpmxrider489 Supporting VIP

    2,149
    39
    Joined Apr 4, 2010
    pittsburgh, Pennsylvania
    My car idling, volt gauge says 13.5. Have you checked the generator relay ( which isnt a relay)? Do you have a ground strap on your alternator? Battery is in the factory location?
     

    Street Build 364  1

    1995 Eagle Talon TSi
    fwd · automatic · 2G DSM

    Street Build 2K  3

    1995 Eagle Talon TSi
    fwd · automatic · 2G DSM
    Loading...
  6. steve

    steve DSM Wiseman

    13,591
    713
    Joined Feb 3, 2002
    Boulder, Colorado
    If your system voltage is dropping to 7v in your log as well I'd check the condition of your battery too.

    2G's ECU will turn off the alternator output to reduce the engine load and improve emissions but it shouldn't let the voltage drop that low and the car can run quite a while with no charge before the battery goes that dead.

    Lets see the log, it will give more clues.
     

    241  4

    2008 Audi TT 3.2 Quattro Roadster
    awd · manual · Misc Vehicles

    198  5

    2002 Audi TT Quattro Roadster 225
    awd · manual · Misc Vehicles

    217  2

    1992 Dodge Stealth RT/TT
    awd · manual · 3000GT/Stealth

    4K  12

    1991 Mitsubishi Eclipse GSX
    manual · 1G DSM
    Loading...
    DJRace likes this.
  7. bo0st

    bo0st Proven Member

    830
    20
    Joined Jan 26, 2010
    Phoenix, Arizona
    Hey there, thanks for the quick reply! I haven't checked the generator relay yet and I didn't look closely enough at the alternator to notice a ground strap. The battery is indeed in the factory location.

    Thanks for the quick reply Steve! It's a brand new battery so I don't believe that's the issue.

    I may have been a little too late in turning on the laptop, I don't think this log has any drops below 13V but let me know if you see anything that would point to a bad alternator:
     

    Attached Files:

    Last edited: Aug 19, 2020

    2K  1

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  8. jpmxrider489

    jpmxrider489 Supporting VIP

    2,149
    39
    Joined Apr 4, 2010
    pittsburgh, Pennsylvania
    I personally dont have a ground strap on my alternator. But I have read people adding one to help with voltage drop. The log looks fairly normal to me. But Ill let someone else speak on that part. Im assuming you checked for loose wires? I would measure the volts at the battery and the alternator to confirm what you gauge is saying. If your alternator measures 7v when your gauge says, I would double check everything in that circuit. But I personally never had a alternator that was bad intermittently. They always just died on me without notice.
     

    Street Build 364  1

    1995 Eagle Talon TSi
    fwd · automatic · 2G DSM

    Street Build 2K  3

    1995 Eagle Talon TSi
    fwd · automatic · 2G DSM
    Loading...
  9. luv2rallye

    luv2rallye DSM Wiseman

    7,793
    702
    Joined Jun 7, 2003
    Minneapolis, Minnesota
    Does your dash battery light go on when the key is first turned on? A burned out light (and bad/missing generator relay) will prevent alternator field coil voltage and so the alt won't charge the battery.
     

    3K  0

    1999 Mitsubishi Eclipse GST
    14.200 @ 95.000 · 2G DSM
    Loading...
  10. steve

    steve DSM Wiseman

    13,591
    713
    Joined Feb 3, 2002
    Boulder, Colorado
    The normal ground path is via the bolts holding the alternator and those holding the bracket to the block and from there via the main block ground cable back to the battery. Just think about all the rust and crud that can get in the way. Installing an alternator ground seems like a really good/cheap way to improve the performance of the electrical system.

    My original alternator in the 1G lasted long enough for the brushes to wear out. The electrical system did some interesting and sometimes exciting things when the brushes would arc.
     

    241  4

    2008 Audi TT 3.2 Quattro Roadster
    awd · manual · Misc Vehicles

    198  5

    2002 Audi TT Quattro Roadster 225
    awd · manual · Misc Vehicles

    217  2

    1992 Dodge Stealth RT/TT
    awd · manual · 3000GT/Stealth

    4K  12

    1991 Mitsubishi Eclipse GSX
    manual · 1G DSM
    Loading...
  11. bo0st

    bo0st Proven Member

    830
    20
    Joined Jan 26, 2010
    Phoenix, Arizona
    Typically no but the light will come on after. Here is a new log and in this one I noticed quite a bit of fluctuation. I turned the car off/on a few times for testing purposes.
     

    Attached Files:

    2K  1

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  12. bo0st

    bo0st Proven Member

    830
    20
    Joined Jan 26, 2010
    Phoenix, Arizona
    7535B65F-A5C0-4157-B687-370C7CD6D1AA.jpeg 9BB3FC38-AF62-4B32-8D92-1F9A2B3BBC76.jpeg
     

    2K  1

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  13. bo0st

    bo0st Proven Member

    830
    20
    Joined Jan 26, 2010
    Phoenix, Arizona
    BCD29736-17A4-4DE6-BF75-A70636922A5B.jpeg

    I noticed that my gauge says 13.6 but ECMlink will report different values so I’m unsure which one to trust.
     
    Last edited by a moderator: Aug 23, 2020

    2K  1

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  14. luv2rallye

    luv2rallye DSM Wiseman

    7,793
    702
    Joined Jun 7, 2003
    Minneapolis, Minnesota
    When the engine is running and the dash battery light is on, the alt is not getting field coil voltage and will not put out.
     

    3K  0

    1999 Mitsubishi Eclipse GST
    14.200 @ 95.000 · 2G DSM
    Loading...
    bo0st likes this.
  15. Jk's97DSM

    Jk's97DSM Proven Member

    199
    42
    Joined Apr 27, 2006
    Norfolk, Virginia
    Buy a legitimate alternator and try to shield it from the heat.
     

    215  1

    1990 Mitsubishi Mirage EXE (SLO CSM)
    manual · Misc Vehicles

    Street Build 537  1

    1992 Eagle Talon TSi AWD
    awd · automatic · 1G DSM
    Loading...
    bo0st likes this.

Share This Page

Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Feal Suspension Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications OHM Racing Raven Fabrication RixRacing RockAuto RTM Racing SouthBay Fuel Injectors STM Tuned Track Decals Track Sculptures VR Speed Factory