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  1. #1
    Join Date
    Dec 2002
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    Gloucestershire
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    5,139

    Default Need more volts!

    My engine has a standard automotive "Lucas" alternator.

    It pushed out the amps but the battery volts never rise above 12.

    The regulator is internal with nothing to twiddle.

    Ideas anyone please?
    I'd rather be naked
    www.mastaclimba.com

  2. #2
    Join Date
    Jun 2013
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    3,128

    Default Re: Need more volts!

    If the voltage is definitely no higher than 12V, the alternator is kaput. Can probably be overhauled rather than replaced.
    If found in the Brexit forum, please return to the real world.

  3. #3
    Join Date
    Jul 2002
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    Home: Kent. Boat: Chichester
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    Default Re: Need more volts!

    Quote Originally Posted by Graham_Wright View Post
    My engine has a standard automotive "Lucas" alternator.

    It pushed out the amps but the battery volts never rise above 12.

    The regulator is internal with nothing to twiddle.

    Ideas anyone please?


    First reaction is that the alternator regulator is defective but there may be other reasons,

    If you are sure that the battery is good a sensible way forward would be to get the alternator tested by an auto-electrician who can then overhaul it , replacing any defective parts.

    Lat time I had a Lucas alternator at different times I replaced the brushes, the rectifier, the regulator and the slip rings. That one, an 18ACR, was easy to work on DIY and I was able to get the parts easily. Not all are so easy DIY.

  4. #4
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    Dec 2002
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    Gloucestershire
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    Default Re: Need more volts!

    Quote Originally Posted by CLB View Post
    If the voltage is definitely no higher than 12V, the alternator is kaput. Can probably be overhauled rather than replaced.
    It is brand new (but still could be kaput I suppose).

    I have a spare.
    I'd rather be naked
    www.mastaclimba.com

  5. #5
    Join Date
    Jun 2013
    Posts
    3,128

    Default Re: Need more volts!

    Has it been run at any point when not connected to a battery? That can kill the reg I understand.
    If found in the Brexit forum, please return to the real world.

  6. #6
    Join Date
    Jul 2002
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    Home: Kent. Boat: Chichester
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    Default Re: Need more volts!

    Quote Originally Posted by Graham_Wright View Post
    It is brand new (but still could be kaput I suppose).

    I have a spare.
    You say it is "pushing out the amps" Where is it pushing them ? If into the battery then either the battery is in a very discharged state, is knackered or your voltage reading is incorrect!

  7. #7
    Join Date
    Dec 2002
    Location
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    Default Re: Need more volts!

    Quote Originally Posted by VicS View Post
    You say it is "pushing out the amps" Where is it pushing them ? If into the battery then either the battery is in a very discharged state, is knackered or your voltage reading is incorrect!
    I need, and you deserve, more info!

    The batteries are fine and, once the engine is running, the alternator delivers around 20 amps.

    There is a possibility I am losing something "down, the line" but the cabling is adequate. I did put a fuse in - your suggestion Vic? That should have near zero resistance.

    I'll take some more measurements.

    I have tapped onto the raw ac for a rev counter but I can't see that would hurt.
    I'd rather be naked
    www.mastaclimba.com

  8. #8
    Join Date
    Jun 2013
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    3,128

    Default Re: Need more volts!

    Where, and with what, are you taking the volt reading?
    If found in the Brexit forum, please return to the real world.

  9. #9
    Join Date
    Jul 2002
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    Home: Kent. Boat: Chichester
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    Default Re: Need more volts!

    Quote Originally Posted by Graham_Wright View Post
    I need, and you deserve, more info!

    The batteries are fine and, once the engine is running, the alternator delivers around 20 amps.
    Something does "not add" up right If the alternator output is only 12 volts it wont be pushing 20 amps into a decent battery. A charged battery is going to be 12.6 or higher and you wont be able to push the amps "uphill"

    Check the volts with a known good voltmeter/ multimeter at the battery terminals and at the alternator output terminals
    Last edited by VicS; 27-03-19 at 11:13.

  10. #10
    Join Date
    Apr 2018
    Location
    Mooring, Faro
    Posts
    1,285

    Default Re: Need more volts!

    Quote Originally Posted by CLB View Post
    Where, and with what, are you taking the volt reading?
    If the batteries are fine, as stated above, they are presumable resting at around 12.8v so surely can't be taking 20 amps at only 12v. Looks like the voltmeter is suspect. If digital, has the battery been changed?

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