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Thread: 735i alternator change?

  1. #1
    Join Date
    Jul 2009
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    '88 735i, '06 RSX

    735i alternator change?

    After having mysterious "check control" and random times having my clock reset, I figured it may have been time to replace my battery. I foolishly did not bother to measure voltage at the terminals when I installed a new battery (and ran the car), only to find my battery dead again. I hooked in my multimeter in series, found a minimal draw of 20mA with the car off and doors closed. Car running on the other hand.....battery voltage was a measly 12.4V on a brand new battery. Clearly, I think the alternator is to blame here. Here is my dilemma. I haven't found a good DIY and the bentley manual is less than descriptive with the removal process. I removed the two back leads off the alternator, upper mounting bolt, the tensioner nut (teeth stripped, ordered a new one), and the tensioner itself (teeth stripped...ordered a new one). I cannot get the alternator belt to slack even all that, and I have no idea where the other bolts are to remove the alternator? Thanks in advance for responses.

  2. #2
    Join Date
    Jan 2005
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    11/88 E32 750iL+98 E36M3
    First unlock the OBC and set on test #9, then you see the voltage. In most cases a new voltage regulator will do the job. I have some new voltage regulators made by Hella on stock for the Bosch alternator with slipring 28mm and also the version for the smaller compact Bosch for the M60 with 14/16mm slipring http://www.bimmernut.com/forum/showt...lternators-new
    For removing the alternator see workshop manual https://www.bmwtechinfo.com/repair/main/
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
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    I'm going to enlist a friend for some help. I will get the bosch 140A alternator from FCPeuro for the lifetime warranty. 198K miles on the original alternator, I think that is a good lifespan. I wish all parts lasted 200K miles

  4. #4
    Join Date
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    11/88 E32 750iL+98 E36M3
    The Bosch alternators on the M30 and M70 last very long, the M60 has a different version, that is the compact version. All a bit smaller, for example the slipring on the M30/70 has 28mm while the other compact version has only 14/16mm. I have the compact version on my E36 M3 installed, lasted only 30kmiles, suddenly the battery light was always dimming, found out that a diode in the rectifier got bad. Replaced it with a used one with new voltage regulator, as I broke the rectifier plastic housing when trying to repair it. Not sure, if that was a single case or if the size down also caused lifetime size down.
    Shogun tricks and tips for the E32 series are HERE!

  5. #5
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    Ok, I got the alternator off... next problem is this absurd alternator pulley 24mm nut that I can't get off. Anybody have a good way off removing? I tried to hold the shaft with a 8mm Allen key and smacked the 24mm wrench a few times to try to loosen it, without success

  6. #6
    Join Date
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    This is a DIY for a compact one http://www.rangerovers.net/repairdet...pair.htm#steps
    That separates in the middle, did you try that?
    Shogun tricks and tips for the E32 series are HERE!

  7. #7
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    I couldn't get the blasted nut off, I took it to a local mechanic and he charged me 10$ to get it off. I had started to strip the shaft 8mm hex slot so I didn't want to risk making it impossible to get off. Putting it back was fairly straightforward, I made sure to use a new tensioner and adjuster toothed nut to make sure it didn't strip and not hold tension properly. I also changed my power steering tensioner + adjustment toothed nut, big improvement there as the belt is nice and tight now, no more squealing and slippage of the power steering pump.

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