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  1. #1
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    Changing alternator brands

    I currently have a Valeo branded alternator fitted. I've replaced the volt reg and still no charge getting to the battery. Also I replaced the battery and checked continuity on the cable and still no joy. So this is leading me to believe the alternator is at fault.
    Could I change from a Valeo branded alternator to a Bosch unit? Or is there something else that prevents me from doing this?

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  3. #2
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    The alternator can be any brand, so long as it works!



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    jojo - thanks for the reply. Was just wondering in case there was pulley's or something that was specific to either brand.

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    What volts are you measuring at the alternator with a multimeter? If it's 14+ volts it should be good.

    It's worth checking the earth points on the engine block and under the battery tray. My new alternator was producing 14.7v but the battery still only gave 12v when the engine was running, cleaned the earth point and got 14.7v when running.

    What problems are you having?

    But yes, any brand alternator will fit if it's correct for the car.
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    Red and yellow battery lights are on the dash.
    I've replaced the volt reg with a genuine Valeo one and still no charge gets to the battery with the engine running.
    I fitted a new battery which, when the engine was running, did not take on board any charge.
    I've checked continuity between the cable and that's all good.

    Car has been running fine since I've owned it last November and just suddenly on Thursday this electrical failure happened.

  7. #6
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    Not into electrics, but can you not check what is coming out the alternator at the alternator rather at the battery to rule out the wiring?

    mark
    S3 2003........REVO..........Stage 1...........218G/S.......÷..........°8..........=..........272bhp ......368Nm.....271 ft lbs

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    epox - not sure how to do this. But yes that would be ideal.
    I've got the alternator out now and found a local place that can bench test the item. So I'll do this tomorrow morning before ordering a replacement alternator.

  9. #8
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    were are based mate i recon alternators for a living stay away from copy units such as rtx they dont last

  10. #9
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    Quote Originally Posted by vala View Post
    epox - not sure how to do this. But yes that would be ideal.
    I've got the alternator out now and found a local place that can bench test the item. So I'll do this tomorrow morning before ordering a replacement alternator.
    Stick the positive probe onto the nut that holds the positive cable onto the alternator and the negative probe on an earth point.
    Audi S3 - 2002MY - Denim Blue - Gone
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    Sham101 - based in Milton Keynes. Have no intention of going with copy units such as RTX. If it needs to be changed I was planning on getting a new item via TPS.

    Tooks - alternator is now off the car. I'll make a note of you suggestion for testing it though, handy to know for future reference. I assume this would tell me the output of the alternator?

  12. #11
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    Yes, just a basic check to tell you what volts it is putting out.

    A couple of years ago, I had a problem where starting the car got gradually lazier and lazier.

    I changed the battery, and after a week or so, the same thing was happening. I was measuring volts at the battery with the engine running, and getting just over 12v, so basically whatever the battery was managing.

    I then changed the alternator for a reconditioned unit, and was disappointed to find I was still getting only 12v at the battery.

    I then read about measuring the output at the alternator, and was getting 14.4v, as it should.

    Thanks to guys on here, I then read about the earth points under the battery tray and also the one on the engine block.

    I cleaned the earth points, the one on the block was quite dirty/corroded, put it all back together and was getting 14.4v at the battery with the engine running. It's been fine ever since, and the alternator was just a recon from the local motor factor, I don't even know what brand it is! It's lasted a couple of years already so I'm not complaining.

    The point is, the earth points are critical to the proper operation of the starting and charging system, I suspect my original alternator wasn't even faulty.
    Audi S3 - 2002MY - Denim Blue - Gone
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  13. #12
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    Yes, just a basic check to tell you what volts it is putting out.

    A couple of years ago, I had a problem where starting the car got gradually lazier and lazier.

    I changed the battery, and after a week or so, the same thing was happening. I was measuring volts at the battery with the engine running, and getting just over 12v, so basically whatever the battery was managing.

    I then changed the alternator for a reconditioned unit, and was disappointed to find I was still getting only 12v at the battery.

    I then read about measuring the output at the alternator, and was getting 14.4v, as it should.

    Thanks to guys on here, I then read about the earth points under the battery tray and also the one on the engine block.

    I cleaned the earth points, the one on the block was quite dirty/corroded, put it all back together and was getting 14.4v at the battery with the engine running. It's been fine ever since, and the alternator was just a recon from the local motor factor, I don't even know what brand it is! It's lasted a couple of years already so I'm not complaining.

    The point is, the earth points are critical to the proper operation of the starting and charging system, I suspect my original alternator wasn't even faulty.
    Audi S3 - 2002MY - Denim Blue - Gone
    VW Polo GTI - 2011MY - Candy White - Here

  14. #13
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    Tooks - thanks for the reply.
    The thing that's odd in my case is that the car has never struggled to start. Even through the winter it would start perfectly.
    Then just one morning on my commute to work the red and yellow battery lights come on. However it still started that morning, prior to the lights, fine.
    I'll clean up and check the connection underneath the battery tray when I'm home later.

  15. #14
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    Good call, but don't forget to clean the engine block one too, follow the wire from the tray to the block.

    I'm no car electric guru, I just got all the above advice from some of the guys on here.
    Audi S3 - 2002MY - Denim Blue - Gone
    VW Polo GTI - 2011MY - Candy White - Here

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    Tooks - will do. My alternator is in getting tested today so we shall see what the outcome is later. Should know early afternoon.

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    Alternator has been bench tested. The rotor has an open circuit. Phew! The fault has been found. New one ordered, and should be with me tomorrow.
    Thank you to everyone who has helped me with this fault

 

 

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