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  1. #1

    Default do i have a short ..??

    i dont know if this the right section but my truck is having an issue during cold mornings.. my voltage will go up and down up and down for about 10 mins until the truck warms up .. when this happens my fuel pump also whines ... i just upgraded my alternator to a 145 amp(didnt upgrade any wires idk if i should of) but this didnt happen until about 2 weeks after i did that so i dont know if thats realevent .. any help is greatly appreciated ...
    2001 Gmc Sierra 2500hd
    -All clear lights with 5000k HID -Spectre cold air intake w/ k&n cone -Cooper dicoverer ST Maxx 285/75/16 -Meyer 7.5ft poly plow E60 pump - 3500 Rear springs-Leveling kit- Backrack-LED interior lights - Pioneer headunit with Alpine type s 6.5 and Polk 4x6 and 12 inch pioneer sub with alpine vpower amp.

  2. #2

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    That may be perfectly normal. My old '05 Envoy (AAFAIK all of the GM360/370) had a "cold morning load monitor" built into the PCM.

    When the PCM detected a load condition (engine load from a charging alt) that it didn't like, it would release the alt from charging duties. As the engine warmed, the PCM allowed the alt to charge without interfering. I don't know why it does this (the engine would still have lots of hp to handle the alt charging load), it must be for emission reasons.

    I haven't noticed my Av doing this, but we have only had a couple of cold days and I may have missed it.
    Ray

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  3. #3

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    ill take a vidieo tomorrow morning so you guys can see it its almost like something cuts out for a split second repeatedly and it only does it for about 10 min so idk

  4. #4

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    OEM wiring should be fine for the alternate, upsized 145amp alternator, by the way...

  5. #5

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    its not a great video but i think you guys can kind of get an idea of what im talking about .. any help would be great .. thanks guys ..

  6. #6

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    idk if it helps but i just discovered that if i drive it during this time , as i press the gas my voltage drops and when i lay off of the gas it goes back up... help please

  7. #7

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    Quote Originally Posted by quicksilver8817 View Post
    as i press the gas my voltage drops and when i lay off of the gas it goes back up... help please
    Again, this may be normal, some PCMs will command the alternator to stop charging under WOT conditions. If you were only feathering the gas and it was falling off, then you have a problem.

    A fully charger battery should test around 12.6 volts, an alternator output is usually around 14.4 volts, when charging. If an alternator is switching from a charge state to a no charge start (and the battery is fully charged) a voltmeter should fluctuate between 14.4 to 12.6

  8. #8

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    This is just a thought, because I want to find out If I maybe got ripped off. When I did my engine swap, I apgraded from a 102 amp alternator up to a 200 amp alternator. I asked the dealer about this, and they said you should have the PCM reflashed to correct voltage spikes that can happen. I fell for it and had it reflashed, It made sense to me at the time. Just curious what your original amperage was on the alternator??

    http://s1191.photobucket.com/albums/z477/noell1947/pbr%20time/
    2004 Chevy Colorado 2wd/4l60e/3.5 Inline 5
    6-PIAA 520 series yellow ion spot lights 85 watts each
    PIAA quattro fog lights w/extreme white/yellow ion bulbs
    Anzo projector headlights/LED turn signals
    LED underbodys 7-color/LED interior lighting
    JET stage 2 performance chip/Magnaflow exhaust S/S
    Recon Big Rig Lights/LED tail lights/3rd brake light
    Putco LED bed lights/BEDRUG
    Goodmark 2" rise Cowl hood/K&N fipk intake
    98-04' Blazer overhead console & floor console
    40/60/40 seat modified to 40/console/40
    33" Cooper Discovery A/T
    16" Pro Comp extreme alloy wheels

  9. #9
    Jr. Engineer Jamm3r's Avatar
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    Default

    Quote Originally Posted by quicksilver8817 View Post
    i dont know if this the right section but my truck is having an issue during cold mornings.. my voltage will go up and down up and down for about 10 mins until the truck warms up .. when this happens my fuel pump also whines ... i just upgraded my alternator to a 145 amp(didnt upgrade any wires idk if i should of) but this didnt happen until about 2 weeks after i did that so i dont know if thats realevent .. any help is greatly appreciated ...
    Tell us more about the upgrade or provide pics.

    If u have an overwound CS130 well that might be enough to explain it as they don't produce as much output at idle as stock.

    If u have an AD244 or a DR44g then it shouldn't do that unless the PCM is telling it to stop charging. It could also be a symptom of early diode failure.

    The stock wiring is 8 gauge which can't carry 145 amps for more than a minute or two without overheating. An upgrade to 6 or 4 gauge welding cable (more flexible) is worthwhile. Some of the better high output alternators have an oversize output terminal to provide better physical support for heavier cable -- the stock stud isn't really heavy enough to support 4 gauge cable properly.
    Minneapolis area - 1997 K2500 regular cab long bed + 8.5' Western Unimount plow + modified transmission + 2nd battery + modified camper charge circuit + 1971 Cayo camper -and- 2004 4x4 Suburban 2500 8.1 + Maxbrake controller + 2nd battery + modified trailer charge circuit + Reese receiver, pulls 30' Airstream trailer

  10. #10
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    You can also use audio power wire to replace the stock stuff, super low resistencia and will be video shielded so you don't get wine through the radio from the engine. Also, is you fuel gauge broken or is your truck empty?? I just ask because if your pump is that loud it's because it's about to go or it's working hard because you have no gas and its cold out.
    99 K1500 Suburban LT "THE BEAST"
    Hypertech III, K&N, true dual
    285/75/16
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