17v too high for a voltage regulator?
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  1. #1
    1000+ Posts parry's Avatar
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    Default 17v too high for a voltage regulator?

    Hey guys,

    Just looking at the log of the 60 laps stint I did on the weekend and noticed the voltage continually creeped up during the 60 laps. Started on lap1 at 14v which is good and eventually went to 17v on lap 60. I have attached the log for your reference.

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    Half way through the 60 laps there was a saftey car and the volyage dropped, so it might be heat related.

    My question really is: Does the volatge regulator guarantee regulation or is there a variance?
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    90 205 Gti Cherry Red(Track Car)
    2009 207gti
    1985 505gti (Shitbox Rally) Sold

    PBs:

    Oran Park: 1:27:9
    Wakefield: 1:05.6 (July 2015)
    Eastern Creek: 1:47 (16V) 2019
    Mt Huntley: 34.44 (2004 stock 205)
    Ringwood: 35.06 (30/10/2005)
    Winton: 1:33.6 (2017)

  2. #2
    1000+ Posts robmac's Avatar
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    Quote Originally Posted by parry View Post
    Hey guys,

    Just looking at the log of the 60 laps stint I did on the weekend and noticed the voltage continually creeped up during the 60 laps. Started on lap1 at 14v which is good and eventually went to 17v on lap 60. I have attached the log for your reference.

    Half way through the 60 laps there was a saftey car and the volyage dropped, so it might be heat related.

    My question really is: Does the volatge regulator guarantee regulation or is there a variance?
    Normal operation is no more than 14.2 volts for an alternator. The typical range is 13.8 to 14.2, optimum being 14.0 volts.

    Many late model alternators have a "sense" terminal. This is connected to the battery directly. If you have several ohms resistance between the alternator output terminal (ie a "thin' cable) and the battery, the alternator output voltage will increased to maintain 14 volts at the battery the voltage at alternator output terminal will be a bit higher.

    17 volts is way too high and will damage an ECU or other electrical gear.

    Where is your test voltage being measured at ? Is it dead accurate? Have you confirmed the accuracy with a digital voltmeter of known origins ?

    I would be checking the alternator wiring, especially the terminals and wiring between the main alternator output and the battery. Also check, if the alternator has one, where the "Sense" lead is connected to, it must go directly to the battery positive and nowhere else.

    Also check earthing between the alternator and the battery negative.

    Last check would the regulator in the alternator or the external connectors to it.

  3. #3
    Fellow Frogger!
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    Don't know the answer Parry, but it is a good idea to run a bigger pulley on the alternator. It wasn't in the mind of the original designer that the car would run at a constant 7000 rpm - hence they don't last long on race cars. The same applies to all ancillary drives, but your PS pump is electrically driven, is it not?

    Tim

  4. #4
    1000+ Posts parry's Avatar
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    Quote Originally Posted by tcusack View Post
    Don't know the answer Parry, but it is a good idea to run a bigger pulley on the alternator. It wasn't in the mind of the original designer that the car would run at a constant 7000 rpm - hence they don't last long on race cars. The same applies to all ancillary drives, but your PS pump is electrically driven, is it not?

    Tim
    Yep Electric PS. So that is ok. I will definately look into a larger pully for the alt after I sort out the voltage. Cant aford a fried ECU
    90 205 Gti Cherry Red(Track Car)
    2009 207gti
    1985 505gti (Shitbox Rally) Sold

    PBs:

    Oran Park: 1:27:9
    Wakefield: 1:05.6 (July 2015)
    Eastern Creek: 1:47 (16V) 2019
    Mt Huntley: 34.44 (2004 stock 205)
    Ringwood: 35.06 (30/10/2005)
    Winton: 1:33.6 (2017)

  5. #5
    1000+ Posts parry's Avatar
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    Rob, the voltage measurment is taken from my ignition output of my relay box directly to the data logger.

    There is a theaded terminal that I am not using on the alternator, that could be the sense wire you are talking about, but that has never been connected from what i remember. Its a good lead to look into. I will check the haynes wiring diag to see if there are any clues.
    90 205 Gti Cherry Red(Track Car)
    2009 207gti
    1985 505gti (Shitbox Rally) Sold

    PBs:

    Oran Park: 1:27:9
    Wakefield: 1:05.6 (July 2015)
    Eastern Creek: 1:47 (16V) 2019
    Mt Huntley: 34.44 (2004 stock 205)
    Ringwood: 35.06 (30/10/2005)
    Winton: 1:33.6 (2017)

  6. #6
    1000+ Posts robmac's Avatar
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    Nov 2004
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    Melbourne / Caulfield
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    19,469

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    Quote Originally Posted by parry View Post
    Rob, the voltage measurment is taken from my ignition output of my relay box directly to the data logger.

    There is a theaded terminal that I am not using on the alternator, that could be the sense wire you are talking about, but that has never been connected from what i remember. Its a good lead to look into. I will check the haynes wiring diag to see if there are any clues.
    If it has been working OK, I would just swap the voltage regulator.

    If it's a problem that has been there from original I would look at the wiring.

    BTW the purpose of the regulator is to maintain the correct voltage regardless of rotational speed. So pulley size won't effect this issue.

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