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Thread: Alternator over charging v8 disco 1998

  1. 26th January 2011, 02:25 PM #1
    pibby
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    Alternator over charging v8 disco 1998

    Had a look at alternator posts and the problems they cover are bearings and/or undercharging. Mine is overcharging. At idle it is putting out 14.3 to 16.5 volts, I even saw it jump into 17 volts. the dash lights are pulsing and the tacho needle is doing the jumps. i checked for firm connection of the wires on the back of alternator. battery voltage at rest is fine.

    It is a mm alternator off a 98 v8 disco part no amr4247. I’ve read the posts about adapting other alternators eg magna. I pulled the back cover off and nothing is blatantly jumping out as being wrong. What’s the chance of it being the voltage regulator and is it testable?

    I came across this oem voltage reg for US$60 which if it fixes the problem and the rest of the alternator is fine is my first preference rather than adapt another one to fit.

    Land Rover Discovery OEM Magneti Morelli Denso Alternator Voltage Regulato

    Thanks,
    Brett.
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  2. 26th January 2011, 02:48 PM #2
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    Blknight.aus
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    check the connection to the back of the alternator for the excite wire voltage while the engine is off then running

    if when the engine is not running but the ignition is on the voltage at that terminal is lower than the battery voltage you have a bad connection somewhere.

    if when the engine is running its at the same voltage as the battery and both are high (over 14.4 14.7 MAX at full RPM) then the regulator in the alternator is shot.
    Dave

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  3. 26th January 2011, 03:13 PM #3
    RoverP6B
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    Yes, I would also say that the alternator's voltage regulator is the problem.

    Ron.
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  4. 26th January 2011, 04:43 PM #4
    pibby
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    How about this scenario – put alternator back on car. Was charging battery fine for a minute or two. Was measuring volts at excite wire and could hear alt load up and would be say 14.2v then it would drop off to say 2.3 volts and load had come off alternator then intermittently it would load up again and excite wire would jump to round 14 volts. Now, not charging and excite wire at 2.3 volts with ign on and also with car running.

    Is this the last spurt of life from the alternator? And does it still sound like the voltage regulator is the part that has failed so I better go and order that reg?
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  5. 22nd April 2012, 09:03 PM #5
    Roachie
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    Suspect Altenator in Tdi Disco

    I too have been having a crazy time trying to make sense of my charging system and have come to the conclusion that my alternator or at least my regulator is stalked...I then thought I'd sidestep the MM brand of alt and put a Bosch or Nippon Denso or something with a better reputation than the OE to no avail. Has anyone with the same idea come up with anything that will come between me and another MM?

    Cheers to all
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