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Just another weird charging issue thread! Please help

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    Just another weird charging issue thread! Please help

    Ok electronic gurus, I have a problem and I would appreciate some help.

    My car is a M30 swapped turbo'd monster that I can not drive because it refuses to charge. I have checked the common items but I will admit that I assumed that it was a faulty +/- 30 year old alternator so I replaced it with a Bosch AL129X 115amp alternator which is identical to the original M30B34 alternator.

    So here is where I am,

    New Battery
    New Bosch starter
    New Bosch alternator

    12.2 volts at the battery and thats with it running or ignition off.
    1.9 volts at the exciter wire on the back of the alt with the key on
    Battery warning light in the dash works well BUT... when the battery voltage dropped on me while driving home at night from out of state 2 weeks ago the battery dummy light never came on. Luckily I have the LCD voltage display in my car so I had the unfortunate experience of watching the voltage count down to my doom which ended up being exactly 8.9 volts at which point the car started to run like crap and shut down.

    That was when I got the new alternator. I installed it and still no charge. And thats when I checked the exciter..... 1.9v. And thats when I went to the ETM to find out about the warning light, which comes on when you cycle the ignition switch.

    Update: still not resolved but more information.

    I checked for voltage at pin 1 on the c101 chassis side of the connector with the key on and the c101 disconnected. I have battery voltage at that point (12.4v). I then connect the c101 and I check for voltage on the engine side of the connection and I come up with 1.9v. Thinking I have a bad connection I once again checked the chassis side with the c101 connected and it now only has 1.9v.

    Is my blue wire grounding out? What would cause a 10 volt drop in power going through the exciter wire when the c101 is connected?
    Last edited by RagtopE30; 02-25-2016, 06:31 AM.
    450whp 524 lb-ft 1988 336ic In progress

    http://www.r3vlimited.com/board/showthread.php?t=250709

    #2
    Bump for assistance


    Sent from my iPhone using Tapatalk
    450whp 524 lb-ft 1988 336ic In progress

    http://www.r3vlimited.com/board/showthread.php?t=250709

    Comment


      #3
      Ok so newest discovery. When the fielding wire is disconnected from the alternator I get battery voltage to the wire terminal and 0.0 ohms resistance through the entire system. No continuity to ground. And I had the Bosch alternator tested three times and it is good.


      Sent from my iPhone using Tapatalk
      450whp 524 lb-ft 1988 336ic In progress

      http://www.r3vlimited.com/board/showthread.php?t=250709

      Comment


        #4


        This website helped me a bit running some tests on the reman alternator I have.

        For me, my charging issue turned out to be the main ground cable from the block to the frame rail. The car charged 'ok' with no accessories on, but when I'd turn everything on, the charging would drop to 12v and sometimes even high 11.x volts.
        -Geno

        '87 325is (s52'd)
        '95 525iT
        '02 Range Rover 4.6 HSE
        '98 Disco 1

        Comment


          #5
          ^ That makes sense because in these cars the grounds are what complete the circuit (rather than the pos like in others) so they have to be clean and able to handle the amps you wanna put through them (even though in reality both are important but just check your grounds to be safe etc etc)


          it's a Kenny Powers quote on wheels

          Comment


            #6
            Ok so I assume that someone else may one day encounter this issue and I should share what I did to fix it.

            After exhausting every other troubleshooting method and coming up empty handed I determined that even though my battery light was working my instrument cluster circuit board had some issues. So I pulled it out and reflowed all the solder. AND it is fixed.
            450whp 524 lb-ft 1988 336ic In progress

            http://www.r3vlimited.com/board/showthread.php?t=250709

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