504 voltage drop issue
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Thread: 504 voltage drop issue

  1. #1
    Fellow Frogger! Pug72's Avatar
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    Default 504 voltage drop issue

    Hi all. For as long as I can remember, the voltage gauge on my 1972 504 hardly ever sits in the black. Especially at night with headlights on - the needle always sits way down in the red. The alternator is the standard sized 35amp and is charging correctly at idle.

    I have never replaced the voltage regulator that is mounted on the firewall. Being 43 years old (the car that is) I am not sure if age of the voltage regulator is causing the gauge to sit in the red.

    The current battery is 4 years old and has no sign of failing. (touch wood)

    Now that I have a stereo with amp, thermo fan, central locking etc, there is more strain on the charging system.

    I am thinking of replacing the voltage regulator as a start...now which one? I have found a genuine Paris Rhone:

    Genuine Peugeot 5761 33 Voltage Regulator 1979 82 504 Diesel 72 76 304 504 | eBay


    and I see Hella make one:

    HELLA Alternator Voltage Regulator/Rectifier 5DR 004 243-051 for TALBOT 1307-1510 Simca 1308 1.4

    Anybody have any experience here? Any advice would be greatly appreciated.

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    Thanks heaps!

  2. #2
    1000+ Posts robmac's Avatar
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    With 35amps available at 4000 RPM alternator shaft speed. And around half that at idle speed you will lucky to cope with the increased electrical load.

    If you are determined to maintain the original alternator you have to accept that the alternator will always battle to hold charge.

    I advocate the pragmatic approach, although chastised by a number naysayers on this forum , I've always found an alternator upgrade to have a positive effect on the electricals of older vehicles.

    There are a number of threads detailing a suitable donor alternators on AF explaining in exactly what required and how to fit and modify wiring. So I won't start yet another, which doubtless will become interspersed on how fix what you already have.

    The total cost outlay is likely to be less than $80 and around half a days work.

    AF google search is your friend. It's near the top of the "page" on the RHS , just under the banner Ad.
    JohnW likes this.
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  3. #3
    Too many posts! JohnW's Avatar
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    There's also the "how accurate is that old voltmeter?" question.

    Robmac clearly knows his onions.
    JohnW

    Renault 4CV 1950 (R1062)
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    National Co-ordinator, Renault 4CV Register of Australia

  4. #4
    1000+ Posts robmac's Avatar
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    I hope there are not any watering eyes.
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  5. #5
    Fellow Frogger! sfrawley's Avatar
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    The voltmeter in my 504 was reading low. I read somewhere that a bad earth between the motor and body could be the cause so I ran a new wire from the head to the firewall and that fixed it.
    Stephen
    '03 P406 HDI
    '16 Renault Master

  6. #6
    1000+ Posts robmac's Avatar
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    Quote Originally Posted by sfrawley View Post
    The voltmeter in my 504 was reading low. I read somewhere that a bad earth between the motor and body could be the cause so I ran a new wire from the head to the firewall and that fixed it.
    If adding an earth cable as you describe "improved" the volt meter reading, Then the original factory installed, cable between the dynamo and the mounting stud on the voltage regulator must not have been intact.

    Because it follows the almost exactly the same path as your "supplementary" earth. It's purpose is to ensure the regulator voltage reference point is the same as the dynamo.
    The less one interacts with rude, ignorant, critical and argumentative members. The more peaceful life becomes.

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