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Problems with electrical (I THINK)???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by DuneRunner, Jun 24, 2002.

  1. DuneRunner

    DuneRunner 1/2 ton status

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    Here goes...

    Yesterday I drove my K5 from SF Bay area to Santa Cruz. (60 Miles) all was good. Started it up after a while. Took 3 cranks to start up. (scratched my head) looked at bat volt gauge. was ok. then drove home. and noticed the gauges where dimming. And I thought That dang Alternator.

    How do I check to see if the alternator is bad?

    New parts and a guess on dates:
    New Battery (10/25/01)
    New MSD 6A box with plugs (11/5/01)
    New Alt (11/28/01)
    New Starter (3/15/02)
     
  2. txbartman

    txbartman 1/2 ton status

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    There are a couple of ways to check your alternator. first, start your rig up. With it idling, disconnect your battery. If it dies, your alt ain't doing crap! If it stays running, that means it is putting out some juice.

    Easiest way from there is to just go down to an Autozone or something and have them test it.

    Another thing I did to gain some confidence in mine was to fire it up and leave everything connected. i then turned on my lights (hi beam) and the blower motor for the a/c on hi (these suck a lot of juice). Then I put a meter across my battery. It was still reading over 12V. Your battery starts with 12V. If you turn on all that you can and are below 12V, your alternator either isn't working under load or just isn't putting out enough juice to keep the battery charged and run your accessories.

    Hope that gives you somewhere to start.
     
  3. DuneRunner

    DuneRunner 1/2 ton status

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    THANK YOU...I can't wait to go home and try that. I got the alt from NAPA Auto Parts not that long ago. So it should have some sort of a warranty.
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    A battery that is fully charged should put out 13.2 volts theoretically. With the motor runing it should read about 14 if the alternator is doing it's job...

    A charging alternator creates a magnetic field. If you are brave fire it up and take a screwdriver and hold it close to the center of the alternator pulley. Watch out for the fan... /forums/images/icons/shocked.gif If it gets pulled in towards the pulley it is charging...if it doesn't it isn't charging.

    Or pull the alternator and take it in to have it checked. Prolly a bit safer.../forums/images/icons/tongue.gif

    Rene
     
  5. DuneRunner

    DuneRunner 1/2 ton status

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    LOL.... Thats a good idea also.

    I notice the gauge was reading right before the RED line I think 16 volts. (far right) And its got me worried. And last night it was droping down to like 8 volts and the lights started to dim. On the dash.
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Could be the internal voltage regulator is fried. I had an alternator do that to me...I'd see the guage over at 18 volts and my headlights would get really bright...5 minutes later it would be normal and then it would do it again. It finally had a little melt down.../forums/images/icons/frown.gif

    I'd pull it and get it tested to be on the safe side. I got stranded 2 hours south of Dallas in the middle of the night...

    Rene
     
  7. Burt4x4

    Burt4x4 3/4 ton status

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    Hey Doony, If you take that alt to a parts house to be tested take your batt with your too and have them check it to make sure you didn't burn a cell in the batt too.I would hate for you to have two bad parts of your charging system!
    Good luck and see ya soon......
    Burt
     
  8. DuneRunner

    DuneRunner 1/2 ton status

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    Thanks Guys. I'll go ahead and pull it tonight and the Batt as well. (burt good thinken) I'm going back to NAPA Auto P. since I got the Alt there. and they seem to know alot more then PepBoys or Kragen Auto parts out here in the Gay I mean BAY area...

    /forums/images/icons/confused.gif Thanks Again Guys. I'll let you know when I do... /forums/images/icons/confused.gif
     
  9. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    By disconnecting the battery cable while the engine is running you risk the chance of blowing a diode in the alternator. Removing the battery cable can cause a spike in the charging voltage which is what could cause the diode to blow. Also if the alternator is computer controlled it cannot be tested off the vehicle like most conventional alternators can with normal testing equipment. It takes a special tester to test those kinds of alternators which most auto parts stores do not have.
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    With truck idling, headlights on, heater on high, check voltage at the single red wire (terminal) on the back of the alternator. If its under 12, you REALLY have alternator problems, if its under 13, I'd consider rebuilding the alternator as well....

    There is no magic to these things, a simple voltemeter will tell you all you need to know. The rebuild kit costs $15 (don't break the case lol whoever said they had) and if the voltage is low, and your idle is high enough (over about 500RPM) then rebuild it, or replace it if its under warranty.

    As has been said, pulling battery cable while running can blow diodes, and make a problem worse, or cause one.
     
  11. DuneRunner

    DuneRunner 1/2 ton status

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    I did some test last night.

    Here you go:
    Cold @ 12. something
    Start @ 14. 5 something holds with no accessories on.
    Low/High Beems @ 12.30
    Heater Full Blast w/ Low/High Beems @ 12.29 and droping
    Finally Radio and ALL ON @ 12.25 and DROPING...

    So I think that there is a slight problem.
    Because Like I mentioned before when I came to a stop.
    The Dash lights went Almost TOTALLY Dim and so did the headlights. It droped down almost to 8 volts on the gauge.
    I put it in Nutural and it bounced right back up...
    I'm driving it tonight and will swing by a Auto Parts Shop and see what they can do...I'll let yall know this evening the verdic.
    THANKS AGAIN. /forums/images/icons/wink.gif

    PS. The worst thing of all is that I can't find the recipt. I burnt it in a fire with old ATM recipts. AAAAAGGHHHHH /forums/images/icons/mad.gif
     
  12. 95 Silverado

    95 Silverado 1/2 ton status

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    be sure the belt is tight and in good condition, sometimes a belt will allow the pulley to slip when a load is applied to the alternator. charging voltage will be good no load, when you turn everything on the voltage will start dropping.
     
  13. UseYourBlinker

    UseYourBlinker 1 ton status

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    Hey Ken sent you a PM.
     
  14. DuneRunner

    DuneRunner 1/2 ton status

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    I'll chech that again. Thanks... /forums/images/icons/ooo.gif

    I did fiddel with those two weeks ago...HHMMM
     

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