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    #1

    Alternator

    Hi everyone. Had some weird issues coming back from vacation. Check engine light tripped on. Code reader wouldn’t connect to DME to read codes. Let it run for a bit, drove it around the block to see if I could feel anything wrong, came back and was able to clear the code - not read it. It didn’t come back. Then I got the red battery light. Thought maybe that was why the scanner wouldn’t connect - low battery. The battery is new and I put it on a charger after I bought it to make sure it was fully charged. Got out the multimeter. Car off I have 12.5v. Car on, it dips to 12.2 and then slowly goes up to 13.7. I thought I should be above 14. Can anyone confirm?

    Thanks.


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    Last edited by sleeks; 06-12-2023, 07:02 PM.
    2004 Silver Grey - Manual - Slick top - Manual Cloth Seats
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    #2
    Mine sits about 13.9V when running. It certainly should not be dipping into the 12.xxV

    Load up electrical ie blower fan on full, rear demister, lights etc and see how it goes at idle. If it starts dropping to mid 12s or lower then it's not keeping up and starting to draw some power from the battery.

    Then raise rpm to 1500 to 2000 rpm and see if voltage comes back up. If it can't get the voltage up then with a big load then definitely alternator related.

    Also check voltage right at battery terminal posts (not just on terminals connected to posts preferably).

    None of this really explains the unable to read codes issue though.

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      #3
      “Car on, it dips to 12.2 and then slowly goes up to 13.7. I thought I should be above 14. Can anyone confirm?​”

      when exactly after starting that it dropped to 12.2v?

      Comment

        #4
        The 12.2 is right when I turn the car on. I think now I clearly need a new alternator. Battery comes on every once in a while. Finally parked it in garage and with a slight rev the battery light comes on and voltage drops to 11.9/12.


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        Last edited by sleeks; 06-23-2023, 05:47 PM.
        2004 Silver Grey - Manual - Slick top - Manual Cloth Seats

        Comment

          #5
          Replace the voltage regulator on the back of the alternator

          Comment

            #6
            Originally posted by ARCHBID View Post
            Replace the voltage regulator on the back of the alternator
            What are folks using for a replacement regulator?

            Comment

              #7
              Originally posted by eacmen View Post

              What are folks using for a replacement regulator?
              Just a moment...
              https://www.realoem.com/bmw/enUS/part?id=BL93-USA-07-2003-E46-BMW-M3&mg=12&sg=22&diagId=12_1085&q=12317792094
              2003.5 MT JB/B - CSL SCHRICK SUPERSPRINT EISENMANN JRZ SWIFT MILLWAY APR ENDLESS BBS/SSR DREXLER KMP SACHS RECARO AR SLON MKRS GSP DMG KARBONIUS CP AUTOSOLUTIONS KOYO

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                #8
                Would this reg work - https://www.fcpeuro.com/products/bmw...eo-12317543917

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