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Alternator charging question

Discussion in 'The Hokey Ass Message Board' started by seesko, Apr 17, 2009.

  1. Before I get roasted I did a search and read all the posts on this subject.
    When I drive my Mercury it shows around 13.5 in the voltmeter. It does seem to fluctuate a lot. Some times it will go as high as 14 or more. If I shut it off and start it up again a lot of the time it reads below 11 volts. Around 10.7 or lower. I have replaced the belts and put an engine to frame ground strap on the car. I has a chrome alternator with a chrome pully. Could that affect it after it gets hot? Sometimes it will pop back up to 13.5 but I thinking it shoudn't fluctuate so much. The engine is a HAMB favorite, 350 Chev :p. Does it sound like a voltage regulator? :confused:
    Thanks guys.
     
  2. sdluck
    Joined: Sep 19, 2006
    Posts: 3,185

    sdluck
    Member

    What alt do you have is it a gm 1 wire.Some need to be rev up after start to energize.
     
  3. There's a plug in with a white and red wire on the side and a post on the back with a heavier wire bolted to it.
     
  4. Thats the reg old GM. If your not sure of the alt. go by the starter gen. shop and have them check it on the car. My $0.02 are going to say the voltmeter is not real correct. If the headlights are good and bright at night I would forget it. IMHO
     

  5. Mr48chev
    Joined: Dec 28, 2007
    Posts: 33,861

    Mr48chev
    ALLIANCE MEMBER

    Ideal charging voltage would be 14.2 but as 325w says, they tend to vary.
     
  6. punkabilly1306
    Joined: Aug 22, 2005
    Posts: 2,655

    punkabilly1306
    Member
    from ohio

    sounds like the style of alternator that needs "excited" to charge...does it go up when you rev the motor?
     
  7. It has Dakota digital guages. The lights do dim when the voltage drops. It seem like revving it when it's down doesn't affect it too much. When I turn on other accessories it does drag it down weither it's reading normal or low. Sometime, like I said it will pop back up by it's self. Maybe I do need to try the rev it up thing. I read it in an older post too.
     
  8. Mr 42
    Joined: Mar 27, 2003
    Posts: 1,215

    Mr 42
    Member
    from Sweden

    13.5 IS ok everything above 13.2 is charging, and remember a battery dont need to be charged all the time, and the voltage will be lower then. But usullay not below 13.2-13.4 Volts


    An Alternator should start to charge at idle or just above. Id take a good multimeter and measur the voltage on the battery post. To see what the voltage is there.
    And go from there.
     
  9. Thanks for all the help guys. I appriciate it:)
     
  10. Shifty Shifterton
    Joined: Oct 1, 2006
    Posts: 4,964

    Shifty Shifterton
    Member

    Take that thing to your local parts store and have em spin it up to see if the internal voltage regulator is working evenly.

    Does this car have a mechanical fan or an electric fan? Older SI series alternators just can't keep up with decent sized fan plus accessories at idle speeds.

    Good luck!
     
  11. Read voltage at the battery terminals with the engine off.

    Right around 12.2 volts indicates a sufficient state of charge.
     
  12. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,285

    d2_willys
    Member
    from Kansas

    Could be one of three things. As posted, use the battery to check your voltmeter, noting this reading. Then check the sense and field wires going to the alternator to make sure they have a good connection. The sense wire is especially important as this will tell the alternator to charge up if the voltage is low.

    The other two things are the internal voltage regulator and the diode trio. Usually the voltage regulator when faulty will do what you say it is doing. The diode trio when faulty (in my experiences) will cause the charging voltage to go high by .6V (ie: 14.2 to 14.8V).

    Like what was posted, take it to a shop and have the alternator tested, both loaded and unloaded.

    My feeling is the sense wire is intermittent, which is where I would start after getting the alternator tested. (Make note as to what the voltage is when being tested)
     
  13. Mad~Max
    Joined: Jun 4, 2008
    Posts: 277

    Mad~Max
    Member

    Ditto, as I was thinking the same thing.

    Pull the clip, and check the sense wire (the one that folds over and goes to the Bat terminal on the alternator.

    Also check the smaller wire on the clip, and trace it all the way back to the idiot light, or the ignition switch. This is the exciter wire.

    In any case, volt meters are real simple, and I believe your voltage is actually changing, and you have a problem.

    P.S. Solder the connections, and use heat shrink tubing to finish the ends.
     
  14. Another possibility ia a loose alt. belt. To check it try to turn the alt. pulley by hand if you can get it to move without belt moving it's not tight enough. When ever you put a load unto the alt. it will actually slow engine down and if belt is loose it starts to slip enough to lower voltage output.
     
  15. I want to thank everyone for their technical advise and really appriciate your time
    Thanks:)
    Mark
     

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