Alternator Light comes on when accelerating

Discussion in 'General Motoring' started by radiantgal, Mar 31, 2006.

  1. radiantgal

    radiantgal Guest

    Hi,

    I have a 1998 S70.

    I was in the mountains last week where the temp was freezing or below.

    Since I have come home the alternator light comes on when accelerating
    from a stop and then and goes off after about 5 seconds when I step on
    the gas.

    My mechanic said battery and the alternator tested ok. He works mostly
    on BMW's
    these days, however started his business working on Volvo's.

    Should I be concerned?

    Any suggestions?

    Thanks,
    Radiant Gal in California
     
    radiantgal, Mar 31, 2006
    #1
  2. radiantgal

    zencraps Guest

    The most logical thing would be to look for a loose or glazed drive
    belt.
     
    zencraps, Mar 31, 2006
    #2
  3. The onlky thing I can think of is that the alternator drive belt must be
    slightly under-tensioned. That is looser than it should be!

    All the best, Peter.

    700/900/90 Register Keeper,
    Volvo Owners Club (UK).
     
    Peter K L Milnes, Apr 1, 2006
    #3
  4. BTW - a good "shadetree" test for a slipping belt is to try to turn the
    alternator by pushing on a cooling vane (right behind the pulley) with a
    thumb. If the alternator moves (and the belt does not) the belt is either
    too loose or worn out.

    Mike
     
    Michael Pardee, Apr 1, 2006
    #4
  5. Besides the belt concern, it's possible the engine ground is bad and the
    engine is getting a stray ground until you make it work and torque to one
    side. The ground is a braided strap under the car in the older models but I
    don't know what it is in the S70.

    Mike
     
    Michael Pardee, Apr 1, 2006
    #5
  6. radiantgal

    User Guest

    I'd guess that the d+/61 wire on the alternator is chafing/chafed
    somwhere and that when the motor rotates under starting load it shorts
    to ground and causes the light to come on.

    Bob
     
    User, Apr 1, 2006
    #6
  7. radiantgal

    Guest Guest


    Although Bob is probably correct --- in a Porsche I own the flicker
    and intermittent light on acceleration was finally diagnosed as being
    a screwed up 'diode block' (or the solid state equivalent) --- the
    alternator was occasionally dribbling out some AC current.

    It might be something to check on after you're sure that the chafed
    wire isn't the culprit, ( --- AC can fry the engine mgmt system).
     
    Guest, Apr 1, 2006
    #7
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