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Reload Thread: New Alt, Low Voltage issues

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    CplCuddles's Avatar
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    Icon9 New Alt, Low Voltage issues

    Hey guys I'm back again with another issue,

    I recently bought a 320 Amp Elite Series Alternator for GM Truck. I was having dropping voltages into the 10s when I decided to buy a HO alt. I replaced my 130amp stock alt with the Mechman and left on my default belt to start. I then started having low voltage at idle issues.

    My Tahoe idles at 500rpm, I'm told this is low, but it has done it since the day I bought it, no issues until now. My initial problem was that when idling (500rpm) I would drop into the high 10s when playing music. I tried to put on a smaller belt as I have seen that is recommended for the smaller pulley, I could not get a smaller belt to fit (even tried 1/2 inch shorter belt, it would barely not fit), So I have the original serpentine belt still on, it seems to be plenty tight. Figuring it was my batterys charge that was the issue, I bought a 750Mah trickle charger and left it on the battery overnight.

    This solved the low voltage at idle issue, initially. A few days later on the 4th of July I had the key on and the stereo on low and my voltages were saying 10V dropping into 9.5V, somehow I turned on my Tahoe and it jumped back up to 14.7V. The next day I couldn't start my Tahoe and had to get it jumped, same voltage issue as the day before. I took my Redtop to O'Reilly to get it load tested, and it came out fine according to them.

    Then yesterday a new problem emerged, while driving I noticed my rpms dropping below 500rpm. I let off the gas and let it drop to see how low it would go and it dropped to about 200rpm and all my lights dimmed out almost completely. I parked and revved for a minute and then turned it off (I was going inside) and it rested at 10.2V immediately after turning my Tahoe off. The low voltage issue seems to be somewhat intermittent was this point. My father who is a mechanic is adamant that it MUST be the alternator. Does this sound like something may be defective with the alternator I received or what else may be causing this? Thanks!



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    Chris McNeeley's Avatar
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    Re: New Alt, Low Voltage issues

    Just stop and burn it down. A v8 that idles 500? Do understand that pulley rotation speed directly effects amperage output. Serious, just stop.



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    Re: New Alt, Low Voltage issues

    Turn down your gains and go get your engine checked. You're having serious issues.




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    Re: New Alt, Low Voltage issues

    Quote Originally Posted by Chris McNeeley View Post
    Just stop and burn it down. A v8 that idles 500? Do understand that pulley rotation speed directly effects amperage output. Serious, just stop.
    Gotta push through my dude. I do understand that pulley rotation directly affects amp output. I figure since the engine is having low rpm issues, that would be causing my voltages issues. People around me keep disagreeing and saying its prob my alt. I'm not a mechanic... at all.

    Quote Originally Posted by The Camry View Post
    Turn down your gains and go get your engine checked. You're having serious issues.
    This is happening even without music, this all started after putting in my new Alt. Gonna get my codes checked tomorrow and see what comes up.



    02 Chevy Tahoe
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    Mechman Elite 320 amp Alt
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    Re: New Alt, Low Voltage issues

    Gotta push through? I just hope your dumb*ss doesn't cause an accident when your sh*t breaks down.



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    Re: New Alt, Low Voltage issues

    Just put your old alternator back on and see if the problem goes away.


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    Re: New Alt, Low Voltage issues

    Quote Originally Posted by Chris McNeeley View Post
    Gotta push through? I just hope your dumb*ss doesn't cause an accident when your sh*t breaks down.
    I don't understand what you're so perturbed about. That it idles at 500rpm? as I said it has always done that. That actually seems to be normal with my vehicle as well as vehicles of the similar type.

    Quote Originally Posted by mikedeezxxx View Post
    Just put your old alternator back on and see if the problem goes away.


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    I'll probably try this, just a pita.



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    Re: New Alt, Low Voltage issues

    Quote Originally Posted by CplCuddles View Post
    I don't understand what you're so perturbed about. That it idles at 500rpm? as I said it has always done that. That actually seems to be normal with my vehicle as well as vehicles of the similar type.



    I'll probably try this, just a pita.
    I have a 14 sierra and it idles at 500 rpms. In thinking of getting a new alt built but **** seeing **** like this makes me not want to. $400 down the drain.




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    Re: New Alt, Low Voltage issues

    Quote Originally Posted by BassDrop View Post
    I have a 14 sierra and it idles at 500 rpms. In thinking of getting a new alt built but **** seeing **** like this makes me not want to. $400 down the drain.
    The way I think about it is that its only a problem if I'm idle for long periods of time and pulling more than I am producing. On average I'm not full volume bassing every time I drive, so I'm really only pulling from reserve during downtime like stoplights. Which I figure if I get a nice reserve bank that won't be a problem at all, because the alt recharges the reserve while I'm not consuming more than produced. I'm not sure that it is the alt that is the actual issue here. Hence why I'm here



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    Re: New Alt, Low Voltage issues

    " somehow I turned on my Tahoe and it jumped back up to 14.7V"

    So, when its running above idle, it reads 14.7v ?? (14.4 to 14.8v is pretty std charging voltage for that series alt. on a GM.) If so, it's probably not a defective alternator. 500rpm is low. 700-900 is std idle speed for that vehicle. Id look into that.



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    Re: New Alt, Low Voltage issues

    Quote Originally Posted by Boominburban View Post
    " somehow I turned on my Tahoe and it jumped back up to 14.7V"

    So, when its running above idle, it reads 14.7v ?? (14.4 to 14.8v is pretty std charging voltage for that series alt. on a GM.) If so, it's probably not a defective alternator. 500rpm is low. 700-900 is std idle speed for that vehicle. Id look into that.
    Correct, If it above about 600rpm it shows perfect voltages. From what I've seen online 500-750rpm seems to be normal. I mean if it truly isn't normal will get it looked into, because it's kind of a pain to have this HO alt and I have idle issues.. lame.



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    Mechman Elite 320 amp Alt
    Kenwood X599
    Crescendo Audio Symphony Coax's
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    Re: New Alt, Low Voltage issues

    Get a smaller pulley. The alt sounds like it's turning so slowly that it's not making any power. You can also adjust your engine idle speed maybe

    does your vehicle have a throttle body with a cable from the pedal?

    ---------- Post added at 11:11 AM ---------- Previous post was at 11:10 AM ----------

    What year vehicle?



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    Re: New Alt, Low Voltage issues

    Quote Originally Posted by Buck View Post
    Get a smaller pulley. The alt sounds like it's turning so slowly that it's not making any power. You can also adjust your engine idle speed maybe

    does your vehicle have a throttle body with a cable from the pedal?

    ---------- Post added at 11:11 AM ---------- Previous post was at 11:10 AM ----------

    What year vehicle?
    It does make plenty of power at 600+rpm, it's seems that it's the low idle that is the issue. I honestly don't know about the throttle body, 2002 is the year.



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    Re: New Alt, Low Voltage issues

    Idk if you'd want to do this, you probably either need to raise your engine idle or get a slightly smaller pulley. I would contact the alt manufacturer and see what they recommend.

    ---------- Post added at 11:29 AM ---------- Previous post was at 11:29 AM ----------

    You don't want to overspin your alt at higher rpms



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    Re: New Alt, Low Voltage issues

    Red tops are starting only batteries and aren't designed for sustained current draw. Sounds like the alt is defective tho.




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