seeking advice on high voltage

Discussion in 'General Motoring' started by newtovolvo, May 5, 2005.

  1. newtovolvo

    newtovolvo Guest

    Can someone offer advice on high voltage?
    I have a 740 (1990) that has a code pointing me to high or
    low voltage. I discovered this while trying to clear out a
    code for another issue. I checked the voltage at the battery
    with the engine running at idle and it was 14.4v. I believe
    that is high but not by much. Tried switching the
    regulator/brush pack (it was the original one that I put back
    in) and it brought the voltage to 14.3v with the engine running
    at idle.

    I believe the battery is good as I measured 12.4v after it
    "rested" for a couple of hours.

    Anyone care to comment on this? I am wondering about the diode
    bridge. I don't know what to expect if I have a bad diode in the
    diode pack. I tried to measure ac voltage and did not get much
    voltage at all, well under a volt.

    thanks for the help
     
    newtovolvo, May 5, 2005
    #1
  2. The voltage will vary with temperature, dropping as the temperature rises.
    14.3 or 14.4 is good for a cool day. Does your 740 have the temperature
    sensor plate under the battery that connects to the alternator?

    Mike
     
    Michael Pardee, May 5, 2005
    #2
  3. newtovolvo

    newtovolvo Guest

    I am thinking of what other info I can pass along.....
    I don't recall seeing anything under the battery when it was
    changed in recent years, only a battery tray as I recall it was
    plastic. I must say I was not really looking very hard, as I was
    focused on changing the battery when I What size is this
    sensor plate in inches? This is a 1990 car, temp sensor sounds
    real sofisticated for a 90.

    Air temp was around 50f maybe 60f yesterday when I made the
    measurements- I guess that could be a cool day?

    Does this still seem normal?
     
    newtovolvo, May 5, 2005
    #3
  4. My 740 -85 had a sensor under the battery.
    I guess this really never worked, the connections where cut by my Volvo
    shop.

    A good idea is to measure the voltage for a longer period when driving the
    car.
    Voltage on my cars goes down to 13,7 or so after a while. I have made a
    cable set for the ciglighter connection and for a multimeter in the other
    end.

    /aw (SE)
     
    Anders Wiklund, May 5, 2005
    #4
  5. The one I have (85 760T) is the full size of the battery tray and has a
    cable coming out the back that plugs right into the alternator. If you
    didn't see that, yours must not have one.

    The voltage sounds about right for the temperature.

    Mike
     
    Michael Pardee, May 5, 2005
    #5
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