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    s52 swap keep ruining alternators

    Hi everyone,

    My obd1 s52 91í 318is seems to be chewing through alternators at an alarming rate. This will be the 3rd Bosch remanufactured alternator that has failed within the last year (around 10k miles). The battery light on the dash has illuminated again, so I checked to see if the battery was charging using a multimeter and itís reading below 12 volts. With the car off, the battery shows around 12.2 volts.

    Iíve checked my alternator wiring and all seems to look fine. I made sure to clean the contacts and ensure all connections were securely fastened upon install of the alternator a few months ago. Iím not an expert when it comes to electrical systems, so is there something else on the car I should investigate?

    Thankfully I have a spare rebuilt Bosch 140a alternator on hand, but I donít want to continue throwing new parts at the car instead of fixing the issue.

    Any help or pointers would be greatly appreciated.

    Thanks,

    Joey

    #2
    Do you have a aftermarket stereo or anything that would put excessive draw on the electrical system? Have you accidentally killed the battery recently by leaving the headlights on? If you have a dead battery and just get a jump without re-charging the battery out of the car, it can overload the alternator and kill it.
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      #3
      I'm still running the stock radio deck and speaker setup, so no aftermarket audio stuff. I can't say I've killed the battery recently either, but I did let the car sit for about 6 months before putting it back into daily driver status a little over year ago with the same battery (battery is dated 2015).

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        #4
        If your reman alternators came from IMC (if you know or not), try ordering from a different source. I had quite a few bad starters and alternators from them in the last couple years (just had to throw away the reman Bosch starter in my E39 on Saturday, coincidentally, a reman part that came from IMC) - would also advise buying a new (not reman) unit and see what happens. Otherwise, it's a fairly basic system, overall. Best of luck and post here if you have more issues.
        Autobahn Motorsport - Portland, Oregon
        @autobahnmotorsport
        '88 M5 | '88 325i | '88 325is | '88 330is | '91 325is | '91 M-Technic 325ic | '93 740il | '03 325it

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          #5
          I know there's an 80 and 140 amp alt for these cars.

          Are you sure you've been installing 140s on the car?
          Originally posted by wholepailofwater
          Q
          :devil:


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            #6
            The problem with reman alternators is they are being sent overseas and they are not replacing the regulators. The windings hardly go bad in an alternator - just take the plastic cover off the back, 2 screws and the regulator pops out. Whenever a customer comes in the shop with a bad alternator, I go straight for the regulator - replace it and 9/10 times it works perfect for years to come, if not then I get a reman alternator and use the new regulator in it.

            As far as them coming from IMC, I am pretty sure all the major suppliers are only using a few different companies and just putting them in their own packaging. Weather it be WorldPac, IMC, Advance Auto etc, most of them are using Cardone or Reliance rebuilds.

            If you have a Bosch, regulator is part number 12311747920, Valeo is 12311747920. If you shop around you can get them for about $50-80.
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              #7
              Just saying, the issues I was having, was after IMC got purchased by Parts Authority, and was exclusively ONLY to parts purchased from IMC. It happened too many times to be considered a coincidence. Just saying, it is definitely a possibility and I'm not the only person who noticed the issues and the frequency of them.
              Autobahn Motorsport - Portland, Oregon
              @autobahnmotorsport
              '88 M5 | '88 325i | '88 325is | '88 330is | '91 325is | '91 M-Technic 325ic | '93 740il | '03 325it

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                #8
                Originally posted by MrBurgundy View Post
                I know there's an 80 and 140 amp alt for these cars.

                Are you sure you've been installing 140s on the car?
                I have tried both in the car. The first was a rebuilt 80a, then I installed a 140a, and currently have an 80a in the car again. The good news is that the 140a isn't much larger than the 80a for fitment within the e30, but the Z3M thicker radiator makes in-car removal very tight (long bolt has just enough room).



                Originally posted by ForcedFirebird View Post
                The problem with reman alternators is they are being sent overseas and they are not replacing the regulators. The windings hardly go bad in an alternator - just take the plastic cover off the back, 2 screws and the regulator pops out. Whenever a customer comes in the shop with a bad alternator, I go straight for the regulator - replace it and 9/10 times it works perfect for years to come, if not then I get a reman alternator and use the new regulator in it.

                As far as them coming from IMC, I am pretty sure all the major suppliers are only using a few different companies and just putting them in their own packaging. Weather it be WorldPac, IMC, Advance Auto etc, most of them are using Cardone or Reliance rebuilds.

                If you have a Bosch, regulator is part number 12311747920, Valeo is 12311747920. If you shop around you can get them for about $50-80.

                Thanks ForcedFirebird for the info on the regulator. When I got home from work, I decided to open up my spare "rebuilt" Bosch 140a alternator, and the regulator definitely did not look new. Looks like a NEW regulator is the first order of business.


                https://photos.app.goo.gl/WBwZVnU9BB6ff1d16
                https://photos.app.goo.gl/8fLYhmCFhte3HZLn9

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                  #9
                  Post back and let us know if that worked out for you! I've yet to have to change out my alternator, but just learned that there are two varieties! Thanks all.

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                    #10
                    I will give some input in the case that the alternators you are buying are of good quality and have their regulators replaced with new. Some issues that may cause premature failure of an alternators output are as follows:

                    -Improper grounding of alternator.
                    -Poor condition of engine ground, this cable grounds all engine electronics including starter and alternator and all sensors. Its very important for this cable to be in great condition.
                    -Defective dying battery. If your battery is 5 years or older, I would consider replacing it. Like mentioned above, if the battery died, it will cause more demand from Alt. Sometimes when batteries die, they can still hold charge, start the car, but be damaged in a state in which they will have difficulty charging up, damaging your Alt in the process.
                    -Short in output cable. There is a heavy gauge cable that runs from the Alt to the starter. If this cable is old and the insulation has broken down, there could be a small bleed to chassis ground, causing Alt to fail in its charging output. This is more rare but not impossible.
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                      #11
                      Thanks for all the advice. As an update, I ordered a new voltage regulator and swapped it into the existing alternator, but that didn't solve the problem. When that didn't work, I ended up going with a known working genuine BMW 140a alternator, swapped the new regulator into that and the car charging system is working once again. Since my battery was pushing 5 years old, I replaced it with a new one as a preventative measure.

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