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1990 K5 w/115 amp alternator...what is yours charging at?

Discussion in 'The Garage' started by Shagnaz, Oct 29, 2003.

  1. Shagnaz

    Shagnaz 1/2 ton status

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    I have never gotten better than 13.5 volt out of my
    alternators 13.25 at the batt. since I have had my truck. I have even bought new ones to see if it would make a difference. NO LUCK.
    Now, I have a winch, extra lights and now windstar elec. fans. With the fans on...the battery is showing 12.75.
    Could this be right or could the cable (that triggers the alt to charge) be old. That wire should be orange and go up to the fire wall.

    Any help would be great. If I could iron out this problem I am going to buy a 200 amp alt.

    Thanks
    Mike B /forums/images/graemlins/usaflag.gif
     
  2. 99firehawk

    99firehawk 1/2 ton status

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    Are you using a multimeter to check voltage ot the factory guage? Also check you grounds at the engine and the frame. Then check your exciter wire on the back of the alt it should read very close to battery voltage with the ignition on. MY dash gauge reads about 13.5-13.0 depening on what I have running, but my voltage at the battery is 13.7 @ idle
    13.5 with the fans on, and 13.9-14.0 @ 2500 rpm
     
  3. 4x4Freak

    4x4Freak 1/2 ton status

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    Is the 13.5 at idle? If so then thats about right, it should be closer to 14 at about 2k miles.
     
  4. 99firehawk

    99firehawk 1/2 ton status

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    [ QUOTE ]
    2k miles

    [/ QUOTE ]

    /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif


    /forums/images/graemlins/rotfl.gif
     
  5. 84_Chevy_K10

    84_Chevy_K10 Banned

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    He means 2k rpm.

    Alt ouput voltage is going to be based on battery state of charge but should always be above 13 v.

    12.6-12.7 is a fully charged battery so I'd say that 12.75 isn't charging the battery very quickly or at all.
     
  6. k5guyva

    k5guyva 1/2 ton status

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    [ QUOTE ]
    Any help would be great. If I could iron out this problem I am going to buy a 200 amp alt.


    [/ QUOTE ]

    What size of battery are you using (cold cranking amps)? If the alternator is running full bore to keep up with the accessories, then a bigger alternator is what you need. But if the battery is too small, or going bad, then a battery is the ticket.

    The battery is what powers the equipment. The alternator recharges the battery. So, my question is what is the battery voltage when the engine is not running? Again, with the engine off, what is the battery voltage as you start to turn things on?
     
  7. Shagnaz

    Shagnaz 1/2 ton status

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    I'm using 2 yellow top Optima batteries. 13.5 is at idle. I will have to check the voltage before I start it.
     
  8. 99firehawk

    99firehawk 1/2 ton status

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    What are you checking voltage with, dash guage or mulitmeter?
     
  9. 4x4Freak

    4x4Freak 1/2 ton status

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    2k rpm. /forums/images/graemlins/ignore.gif
     
  10. POWERMAD

    POWERMAD 1/2 ton status

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    Here is a quick run down on the charging system.
    A 115 amp alternator should be putting out 115 amps at 12 volts.
    The charging system will generaly show between 13 and 13.5 volts at an idle no matter what the amperage of the alternator.
    With your fans on and showing 12.75 volts sounds normal. (what is the amperage of the fans?)
    Think of the battery as being filled with water. the flow of current (amps) being how much water is flowing and the voltage as how much water there is in the battery.
    Does that make sence?
    You need a way to measure amps to see how much of a load your system has on it.
    A .25 volt drop from the alternator to battery is with in specs.
    What size wire are you running from the alternator to the battery? I like to run 10 gage wire.
    From what you posted it sounds to me that your system is operating normaly.
    When my fans kick on it will pull my batt down to 12.5 or so for a bit then it will recover and go to about 13.
     

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