Ideas on a 406 V6 alternator/charging issue
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  1. #1
    Fellow Frogger! ajpolden's Avatar
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    Apr 2004
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    Launceston, Tasmania
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    Default Ideas on a 406 V6 alternator/charging issue

    Hi guys

    I've got a bit of a curious problem with the charging circuit on my 406SV. In short, the dashboard charge light illuminates after driving for a bit, and remains lit until I'm almost stopped. When the car is not moving, the alternator is charging fine: 14.2V across the battery terminals. It doesn't change with engine speed, only road speed - driving slowly after stopping doesn't seem to re-trigger the problem.

    Any ideas what might cause this kind of intermittent behaviour, before I go ripping the alternator out, or worse still, paying someone a fortune to fault-find? Everything seems pretty well seated and secure in the battery holder, and there's no other loose cabling that I can see. Of course, the alternator is pretty well hidden in the engine bay though. There is quite a bit of grime from a weeping rocker cover on the front of the engine and surrounding parts, so I wouldn't be surprised if that was part of the issue, but why not when stationary?

    The slightly longer version of the story goes thus: I was out one day about a year ago, and I saw the charge light on the dash flickering, with an accompanying relay chatter. This continuted most of the way home on a ~30 min drive, and once home (and stationary) it stopped. The batttery was charging, and no amount of restarting the engine and driving it would make the problem come back. That was until last week, when the same behaviour occurred on my way home, though this time, I noticed the behaviour mostly occurred when pointing the car downhill, and almost not at all when the car was pointed uphill. This time though, it's here to stay, at least until the car stops moving and I'm able to whip out the multimeter.

    I've determined via a wireless multimeter connected to the battery that the problem is indeed affecting the battery charging, only 12.something volts when driving, so not something that merely affects the dash light.

    Any ideas, froggy fans?

    Andrew

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    Current:
    1999 406SV (D8)
    Previous:
    1986 BX19GT

  2. #2
    Fellow Frogger! Roland's Avatar
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    May 2005
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    Perth
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    Default

    I would suspect that the cause of the problem is the brushes in the alternator.

    How many Ks has the car done?

    The brushes will be worn down and are no longer being pressed by the springs hard enough to contact the armature properly.

    The addition, the dust and the oil/grime situation is probably preventing the brushes from sliding in their housing as well.

    So, literally, the brushes are bouncing off the armature at speed and only contact reasonably well when the engine is turning at idle.

    Solution:
    Remove the alternator and have it rebuilt (new brushes and bearings and a clean and test) or possibly just contact someone like EAI and check the price of a brand new unit.


    Cheers
    Roland

    Land Rover Discovery 4
    406 Coupe D9 - Manual (2002)
    406 SV Sedan D8 - Manual (1998)
    307 Hdi Estate - Auto - (2007)
    307 Hdi Sedan - Auto - (2007)
    505GR Estate - Personal Import from UK 1971cc Manual (March 1986)
    405 Mi16x4 (all the parts ready to install into the LeMans body)

  3. #3
    Fellow Frogger! ajpolden's Avatar
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    Apr 2004
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    Launceston, Tasmania
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    Default

    Thanks for your input. I imagined given it seems ok regardless of engine speed that it would be more sinister, but I guess your suggestion is plausible. The car has done nearly 370k kms, so it's probably time for a new set of brushes at least

    Sent from my E5823 using aussiefrogs mobile app
    Current:
    1999 406SV (D8)
    Previous:
    1986 BX19GT

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