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Power Drop

Discussion in 'A4/S4 forum(B5 Chassis)' started by ScottD3, Oct 8, 2013.

  1. ScottD3
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    ScottD3 I want your faulty electronics

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    [Oct 8, 2013]
    I opened all my windows the other day and noticed my power dropped down. Its never done this before.

    Any ideas what it could be?
    Draw from the windows, so its normal or an actually fault with the Alternator or something?


    Little Video.
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  3. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 8, 2013]
    The windows know to stop by stalling out the motor and detecting excess current draw. I wouldnt have thaught one window would cause that much drop, but all four might.

    What happens if you try again with the engine at 1500rpm rather than idle?

    Similarly what happens if you put other electrical things on, like lights, heated seats etc?
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  4. ScottD3
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    ScottD3 I want your faulty electronics

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    [Oct 8, 2013]
    It drops.

    I've never noticed it before and something that moves like I would have noticed.

    Most of this year the power needle has been moving around a lot.
    I'm bracing my self for the alternator to pack up but want to make sure it is that and not something else going pop.

    I was stuck in traffic on the M25 couple of weeks ago and the power dropped down to about 12.5v, pulled away and carried on my trip and it went back to just shy of 14v.
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  5. PAULF
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    PAULF Active Member

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    [Oct 8, 2013]
    Scott,

    It sounds like your brushes are on the way out.

    I did the Avant earlier this year - quite a simple job although my commutator was worn badly.

    I used a spline bit in a drill to spin up the alternator and using a flat file turned down the shaft.

    Finished it off with wet and dry and put in the new brushes - all good.
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  6. ScottD3
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    ScottD3 I want your faulty electronics

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    [Oct 8, 2013]
    Aragorn, revs about 1500 as you said and it still drops.

    Dave, where did you get the brushes from?
    I'll try that first.
    Might as well for a new belt and tensioner. The belt is looking a bit warn.
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  7. boost-addict
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    boost-addict Member

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    [Oct 9, 2013]
    if you have a halfords near you get your charging system and battery checked, since we swapped contracts from bosch to yuasa we took delivery of a expensive bit of kit that also resets and programmes stop start vehicles.

    it will tell you the unloaded and loaded voltage of your alternator, check the starter motor and starting crank amps under starting conditions. and then finally check the battery, you may have a failed cell. or even have a sulfated battery. which can cause low volts/amps, or cause the battery to resist the transfer of electrons which would make the voltage drop as your using more then the battery can put out at that time

    fyi my window or even all windows going up/down dont even draw that much power at idle
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  8. PAULF
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    PAULF Active Member

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    [Oct 9, 2013]
    I got my brushes ( it's a brush pack) from a local auto electrical factor - I can't remember the price but think it was around £20.
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  9. ScottD3
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    ScottD3 I want your faulty electronics

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    [Oct 9, 2013]
    Boost-addict, if Its free I might as well go see Halfords and see what they say. If they say its the alternator I'll do what PaulF said.

    Thanks. :)
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  10. B5NUT
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    B5NUT Well-Known Member VCDS Map User

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    [Oct 9, 2013]
    Replaced my alternator this year, got a new one from ECP when they were having one of there discount weeks so got it for just under £90, the bushes were just about gone, the commutator was badly worn and the bearings did not sound great but to be fair it had done 270K, was surprised it was still working.
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  11. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 9, 2013]
    Why start farting around with the alternator until you've put a multimeter over the charging circuit and figured out exactly whats going on...
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  12. ScottD3
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    ScottD3 I want your faulty electronics

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    [Oct 9, 2013]
    Read above.
    I am.
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  13. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 9, 2013]
    Taking it to halfords is not what i was proposing! The monkeys there will just clip something to the battery and do some tests you can do yourself (and have already partly done yourself!)
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  14. ScottD3
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    ScottD3 I want your faulty electronics

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    [Oct 9, 2013]
    But its cold and wet out side now.
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  15. boost-addict
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    boost-addict Member

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    [Oct 9, 2013]
    can i say, (as i work for halfords) that something they clip to the battery, can tell exactly the problem with the battery, be it bad cell or it sulfated and has lost cca, also itll check the alternator under load and not under load, and it will also time the cranking time to make sure the startermotor isnt the cause by drawing more amps then it should be,

    it is free, and im far from a monkey. yes granted 9/10 people at halfords dont have a clue, but you will find experineced guys that have a love for cars, (like me) infact we have 3 at ours, my self , my brother and a older guy who is about 50 knows hes stuff, and strips and repairs/restores land rovers in hes spare time.

    i know halfords got a bad name with ripspeed, but i feel (and not just saying coz i work there, but) they do proved a great service for those that dont have a clue how to fit a bulb or blade and far less costs then a garage.

    any way go to halfords and ask for a battery ans charging system test, dont let them use a green bosch tester as those are **** compared to the midtronics kit all halfords should have
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  16. boost-addict
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    boost-addict Member

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    [Oct 9, 2013]
    any way heres my car.

    1st drop is one window, 2nd is both fronts and then 3rd is all four

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  17. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 9, 2013]

    My suggestion to scott was that it could be a bad connection or high resistance joint between the alternator and battery. In those cases, testing at the battery would show the alternator is faulty under load, when infact its not. A mate of mine had all sorts of alternator issues on his bora, battery not charging and dash warnings about alternator etc which came and went at random, and eventually we discovered the output terminal on the back of the alterantor was all corroded and manky. Cleaned it up and problem cured.

    I worked at halfords myself when i was young as a dedicated Audio fitter, so i agree that there are folk there who know their stuff, but i also know many folk that work there dont have a clue!

    The halfords test might be useful, but it wont be conclusive.
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  18. boost-addict
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    boost-addict Member

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    [Oct 9, 2013]
    yer its still the same, but most eople at my place are trained to fit bulbs blades and batteries if you like

    im there dedicated audio fitter. but also good with electrics so i tend to do other things involving the electrical system!
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  19. ScottD3
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    ScottD3 I want your faulty electronics

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    [Oct 9, 2013]
    Yours even drops off higher than mine.

    Any free check is worth it I think.
    I'll do my own checks but if I'm passing a Halfords (Shop or garage?) I'll pop in and say I want a midtronics test on my charging system please or something.
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  20. boost-addict
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    boost-addict Member

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    [Oct 9, 2013]
    shop,

    yours drops considerably more then mine, i have a 690cca calcium battery and 120 amp alternator, i very much doubt mine drops as much as yours,
    i watched both and yours spikes heavily underload.
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