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"Exciting" the Alternator

Discussion in 'Technical Q&A' started by marco246, Nov 17, 2006.

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  1. marco246

    marco246 Formula Junior

    Mar 25, 2004
    288
    Hawaii
    Full Name:
    Mark
    #1 marco246, Nov 17, 2006
    Recently my 328's charging system has not been keeping the battery charged. Below 3000 rpm the tell-tale red battery charge light on the dash would illuminate. My mechanic and I worked on the car today and found the alternator belt loose. Since it was showing some wear, we (and it took both of us) replaced it with a new one and tightened it up. On running the engine up to 4000 rpm in the garage we found the alternator was not charging at all. So the belt apparently was not the problem. I decided to buy a new or rebuilt alternator and drove home.

    On the drive the red light illuminated whenever the revs fell below 3000, just as before. The last three miles wind uphill to a dead end, and as usual I ran at high rpms (7000 max today) just to enjoy the music. On pulling into my garage I noticed the red light was off and the alternator was apparently charging at idle. Called my mechanic, who said it was possible the alternator had been "excited" by the higher rpms and was now working. We agreed I'd drive it a couple of times over the weekend to see if it's working for keeps.

    I do not doubt my mechanic, who has a lifetime of experience with this stuff, but neither do I want to clutch at straws. Anyone out there with an informed opinion? In any case, I ought to know for sure by Monday.

    Cheers, Mark
     
  2. smg2

    smg2 F1 World Champ
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    Apr 1, 2004
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    #2 smg2, Nov 17, 2006
    rebuild it, either the rectifier bridge is on the way out or the diode pack is failing. only a matter of time. any good shop should be able to rebuild for around $100. i just had mine re-done and upped the amps to 110. ill dig up the paperwork with the all the bosch part numbers so you can have it as reference.
     
  3. marco246

    marco246 Formula Junior

    Mar 25, 2004
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    Mark
    #3 marco246, Nov 18, 2006
    smg2,

    Thanks for the reply. A parts list would indeed be welcome. I had not considered having the alternator rebuilt locally but will look into it.

    Cheers, Mark
     
  4. 348pilot

    348pilot Rookie

    Sep 18, 2006
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    Phil Price
    #4 348pilot, Nov 18, 2006
    Try tickling its nuts.
     
  5. ernie

    ernie Two Time F1 World Champ
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    Nov 19, 2001
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    #5 ernie, Nov 18, 2006
    LOL!
     
  6. Steve King

    Steve King F1 Rookie

    Feb 15, 2001
    4,367
    NY
    #6 Steve King, Nov 18, 2006
    Usually if I buy a new , used or rebuilt alt or starter I would bench test it prior to putting it in. These results will tell you if it is working properly and then do the install. This does not sound right unless there were something wrong with the brushes or the rect. bridge. Take it back out and test it.
     
  7. marco246

    marco246 Formula Junior

    Mar 25, 2004
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    Mark
    #7 marco246, Nov 18, 2006
    348 pilot,

    I knew it was just a matter of time. . . .

    Steve King,

    Sorry I was unclear. We replaced the alternator BELT, not the alternator. If I should have to buy another alternator I'll take your advice re the bench test. Thanks.

    Mark
     
  8. Steve King

    Steve King F1 Rookie

    Feb 15, 2001
    4,367
    NY
    #8 Steve King, Nov 18, 2006
    Sorry I guess I misunderstood. But if you are not getting 12-14 volts at 1000 rpm then a belt ain't going to do the trick. You would need to pull the alt.
     
  9. marco246

    marco246 Formula Junior

    Mar 25, 2004
    288
    Hawaii
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    Mark
    #9 marco246, Nov 18, 2006
    Just did a high-speed run to check out the alternator. It did NOT Get "excited." Still won't charge below 3000 rpm. So I'm going to have to replace it. From the diagram I have, it looks like the voltage regulator is separate from the alternator. It has its own part number. Anyone know whether that typically is replaced along with the alternator?

    Cheers, Mark
     
  10. Steve King

    Steve King F1 Rookie

    Feb 15, 2001
    4,367
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    #10 Steve King, Nov 19, 2006
    The VR is built into the alt. Take it to a Bosch rebuilder which most autoparts store know. Have them update it to the max amp rating which I believe is 85 amps. Should cost between $100 - 130. Just make sure that they dont lose the pulley. There is most likely a Bosch replacement off the shelf alt but I don't have a number. The only Ferrari uniqueness is the pulley.
     
  11. carlrose

    carlrose Formula Junior

    Nov 25, 2003
    327
    #11 carlrose, Nov 19, 2006
    Hi Mark,

    The voltage regulator on the 328 can be replaced without removing the alternator from the car. You'll have to remove the orange vent hose & bracket, then reach up from underneath behind the alternator. Not too difficult.

    I have the Bosch voltage regulator unit recorded as part #1197311023, which is listed at www.importec.com as #F4010-39368 for $26.10.

    I have the entire alternator listed as Bosch #0.120.469.641, but typically these can be rebuilt. Ask your particular rebuilder if the voltage regulator is replaced as part of the procedure.

    www.italiancarparts.com lists an exchange at:

    328 & Mondial 3.2 models 1986 on: #FR121761r $429.95*exchange

    Apologies, don't have a cross-reference.

    Best,

    Carl
     
  12. marco246

    marco246 Formula Junior

    Mar 25, 2004
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    Mark
    #12 marco246, Nov 19, 2006
    Steve and Carl,

    Thank you very much for your information and advice. I'm checking out the usual sources re prices for rebuilt alternators now, and tomorrow I'll query a couple of shops here that might rebuild locally.

    Carl,

    I am sending you a PM regarding your recent water pump replacement. Couldn't help but notice the dried crud on my water pump when we were wrestling with the alternator the other day. I've got a bad feeling about it. . . .

    Cheers, Mark
     

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