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Help needed. Big time.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by txguy, Oct 6, 2001.

  1. txguy

    txguy 1/2 ton status

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    Location:
    Round Rock (Austin) Tx
    Good morning/afternoon all. First off, I am electrically inclined enough to wire a car stereo. After that, well... Anyway. I have a brand new battery, new 94 amp alt, and new blower motor. I have severe voltage fluctuations (sp) between 8.5-13 volts. Couple of questions. When you go from park, to drive, reverse or neutral does anything happen to the electical system other than a slight RPM drop. Is there something in the tranny, or else where that engages electrically that would draw 10-20 amp maybe? (guessing based on the voltage drop) And after that when engaging 4 wheel hi/lo from 2wheel high is there something electrical that would engage again on top just being in drive/reverse/neutral? I get another drop when I go into 4wheel drive mode. Other than that, I get fluctuations by several volts based on sitting still at a light, or driving. Sometimes its low at idle (9 volts), other times its about 13 volts. On a different day, same electrical items running (headlights, no offroad lights, interior fan on vent, not a/c mode, and in gear) I will get a great reading at 13 volts at idle, and then as I go it drops to 8.5 volts-10 volts at speed. This is random and fluctuates based on the position of the moon, time of day, and what mood the truck is in. I have noticed in the last 3 days, when I am driving at night the lights flicker from dimmer, to not so dimmer when I go over a small bump in the road going down the highway. All along I have wondering if its wiring loose or something like that. Now I kinda think with the bumps and the flickering that is surely is. However, I just got an electircal system check, he said my brand new alt is bad. I told him it was new, and the old alt did the same behavior. In fact when I took it off, it tested good. Now, the new one may have aproblem (burned up maybe). At this point he told me to replace the alt. Why? I really don't think thats it. He said that there is too much load on it. The OEM is around 70 amps I believe, this one is a 94 amp model. Yet, the problem is the same, etc... I informed him of this. Either he is wrong, or does not want to deal with digging into the problem more to find the issue. He said it would be about a 150 bucks to pull the stuff by the volt meter on the dashboard to start tracing and checking the wiring. I don't want to get into something that because a lost cause, and spend bucks and get no where. At the same time, I have thought it may be easier just to rewire a few things... (battery to starter area, alt to starter area, the wiring from the engine area to the inside fuse block) and see if that helps). How hard is it to rewire those areas? Also, has anyone had these issues before? That guy said several times, he swears the alt is the problem, that and when good it does not kick out enought juice. I don't think thats it, because its 25 or so above OEM rated alt... Anyway, please!!!
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Are you checking voltage with a volt meter, or just watching the stock gauge? Use a voltmeter at the battery to check this stuff. But if you are getting fluctuation even with a voltmeter, you probably have a loose wire somewhere. Almost every electrical problem on these trucks comes down to a bad ground : )

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     
  3. txbartman

    txbartman 1/2 ton status

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    I recently installed a new 180A alternator. I have noticed severe inaccuracies with my voltmeter in the dash since the install. Under most conditions (like going down the highway), my dash voltmeter reads around 8-9. At fast idle, it will show abou 13-14. But it quickly drops. However, the battery is at full charge. I know that the alternator can't be bad because if it was, my battery would be toast by now. I wonder if it has something to do with the wires I cut when putting in the new alternator. It doesn't use the same one as the stock alt did. I have decided not to pay any attention to mine.

    However, my lights stay bright all the time and they don't flicker. I would agree that it sounds like a bad ground. But, if not, rewiring the battery, the alt and that stuff isn't hard. If you do, use thick, fine strand copper wire. I used 4GA on mine (check it out through my link). You can get it at most custom stereo places.

    Brian
    Check out <a target="_blank" href=http://tx85gmcguy.alloffroad.com>My Jimmy</a> with all her projects!
     
  4. Derf00

    Derf00 1/2 ton status

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    Based upon what you have said about bumps and dimming, all points to a bad connection. Start at the battery and work towards the fuse block and check all the connections. Pull the fuse block and make sure all the connections are good.

    Derf00

    "A WISE MONKEY NEVER MONKEYS WITH ANOTHER MONKEY'S MONKEY."
     
  5. TXBIGFISH

    TXBIGFISH 1/2 ton status

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    Location:
    Sachse TX
    I ran into something simular last week, it turns out the battery ground to the block was corroded at the block. I cleaned it up and put a new negative cable on and problem solved. You didn't say if you hooked a voltmeter to the battery when it was runnning and what it was doing. I could be the voltage regulator, but most GM's are internal to the alternator. Also Start at the battery to stater and alternator and do a continuity check with a good voltmeter, it should have a coninuity beep, or tone. Hope this helps,


    &lt;*)))&gt;&lt;

    81" GMC Jimmy.............stock for now!
    I see a 6 inch lift in the near future!
     

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