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Alternator Going Bad???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by NateAz87k5, May 19, 2002.

  1. NateAz87k5

    NateAz87k5 Registered Member

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    Phoenix, AZ
    Here is my problem. The battery is not holding a charge while I have the Head lights on and the A/C going and the stereo going. If I sit at idle to long the truck will die and there isn't enough juice to start it again. Now normally I dont have any problems but when I have the A/C running it really drains the charging system. My meter will reads normally around 13 amps but you put on the lights and it dips to about 10 same with when you turn the AC on. What gives. Now I have driven in new vehicles and the amp meter never flinches when you turn on the A/C, Head lights, or stereo ect. Just stays around 14 amps. Thanks for any responses.
     
  2. 76JIMMYWPG

    76JIMMYWPG Registered Member

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    Yep, sounds like your alternator, now if you are anything like me, I have a thing for loud music, along with other power draining items, A/C, fog lights,etc.
    What I am doing is there is a guy locally here where I live that does alternators and starters, and as he said, these trucks come with a 35 amp alternator normally, and heck, my turn signals make my voltmeter dance, nevermind my tunes! He's going to install a 90 amp GM alternator (rebuilt by him BTW) with a smaller pulley and larger feed wire (due to higher current) for 100 bucks!
    hope this helps!
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Your profile isn't filled out, but judging by your username, I assume you have an '87, which uses a volt gauge, not amps.

    You need to get a voltmeter and measure voltage with it. The stock gauge is fine, AS LONG AS you make sure you understand that when it says XX volts you may have something different. It doesn't matter, as long as you know that anything under XX on the gauge is under 12 volts. Make sense? Basically I'm saying the gauges are relative...if something changes from normal, look into it.

    That said, check voltage at the battery, and if you wish, at the back of the alternator. (single wire) Both under load (lights on, heater on high, etc) and no load. In neither cases should it drop below 12 volts, and it should ideally be in the 13-14.5V range. You can get a rebuild kit for the alternators for about $15, and they aren't hard to do at all.
     

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