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High Amp output on startup ???

Discussion in 'Chevy Trucks' started by scottL, Oct 23, 2013.

  1. scottL

    scottL PlowSite.com Addict
    Messages: 1,613

    Stuck on this one....
    2007 2500 HD 6.0 gas. Has the HO alternator, dual batteries.

    On start up the meter on the console reads high 14.8/15 volts. This holds true for 5-10 minutes. This seems to be a new thing recently.

    So, being an older truck now I swapped both batteries for better AGM style. Cleaned and checked all grounds and every power cable I could get too.

    I then had the dealer check the truck out .... When I first brought to them it was running HO amp's for basically always. The 'mechanic' eventually took off the plastic top engine decoration and then the amp's dropped. He had no idea what happened and I'm out $90 bucks.

    I went to advanced auto and we did a starter test. Amp draw was well over 200 so I replaced the starter and battery cable leading to it.

    Still same problem.

    The only thing I can add is I have run back and forth between the batteries with a meter and sometimes my accessories battery ( the front one ) is getting 14.8 v while the primary start battery ( the back one ) is only seeing 12.8 v. This is random when it happens.

    :dizzy::cry: Thoughts?????
  2. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,391

    so the meter in the tk is reading that high correct?
    where abouts in the area, I wont charge you 90.00 ill do it for 89.99 bahahaha
  3. scottL

    scottL PlowSite.com Addict
    Messages: 1,613

    Volt meters on both batteries and the the gauge.

    Heck why not - do you have a CC machine? Since Chevy has gone over to independent mechanics you get what you get and mostly they are average at best. It seems if the computer tells them the exact issue they can figure it out ... if they have to change something it is just sloppy now.
  4. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,391

    So meters on the batts. Now my only question for the moment is this. Is the pass side batt still hooked up to the solenoid?
  5. scottL

    scottL PlowSite.com Addict
    Messages: 1,613

    Yes. It is a factory installed dual batter setup. So, it receives direct current from the alternator. It is also hooked up to a relay aux battery device.
  6. crete5245

    crete5245 Member
    Messages: 61

    Have you checked the connection at the back of the alternator? How big of a wire is coming off the alternator? You might want to go to a bigger wire size this will help flow more amps.

    The alternator is going to charge at a higher rate for the first couple minutes after you start the car to recharge the energy lost during the cranking time to start the engine. I would not be to worry about it putting out 14.5-15 volts for the first 5-10 minutes, as long as it dropped back into the low 14's .
  7. scottL

    scottL PlowSite.com Addict
    Messages: 1,613

    Yes, the deal mechanic said the first few minutes too. However, the fact that is raise the dash meter at all is new. It is random but sometimes it will keep the voltage running high for 20-30 minutes, sometimes is never comes down until a few start stop cycles, sometimes it drops voltage with in 5 minutes.

    It's not acceptable. Something is failing.
  8. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,391

    Well ill say this as far as the dash gauge. Don't always believe it. They are off more then you'd believe it
    Now. Here's what I would do. Get rid of the factory solenoid for the 2nd batt and wire that one in parallel. Remember this h.o. alts are pretty much designed to put out high output all the time no matter what. So the regulator is putting out 14.6 all the time, you computer tell the alt it needs more b/c of starting and guess what the alt does exactly that puts out more.
    Now just for grins ck the connectors,,,,pos and gnds all over that engine bay. Pull the heat shrink back and make sure no green stuff is hiding in there.