High Voltage

Discussion in 'GM Electrical Tech' started by BRB46, Jan 26, 2014.

  1. BRB46

    BRB46 Rockstar 100 Posts

    Just want to know what voltage is considered to high. I know fluctuations are normal but over the last couple weeks mine on the factory volt meter is above 14. So i installed a digital voltmeter and it is reading 15.5v at idle and up to speed. That seems too high. I also get a warning chime randomly but no info on the DIC and no other warning lights. Don't know if they are related. It is an aftermarket NAPA reman alternator which has been installed for almost 2yrs. I believe the stock one was 105amp and this one is suppose to be the same. Should I replace it or is there no need for concern. Don't want an electrical fire. Occasionally it would run that high but then settle down just a bit over 14 and sometimes under.
  2. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Sounds like the alternators internal voltage regulator is going or gone bad, along with dangerous spikes to electrical parts on the truck you also have a very real probability of overcharging the battery and getting a battery melt down.
  3. BRB46

    BRB46 Rockstar 100 Posts

    Thanks. That doesn't sound too safe. Looks like I should swap it out. Well I just swapped out the alternator and the voltage dropped down to 13.2v. I didn't drive it yet but ran up the RPMs to 1500 for a couple minutes while switching loads on and off. It started at 15v and slowly dropped down to 13.2. I presume because battery was slightly over charged. So hopefully that will solve the issues. Thanks.
    Last edited: Jan 26, 2014
  4. TRPLXL2

    TRPLXL2 Epic Member 5+ Years 1000 Posts

    My 2013 camaro stays around 15.4v, I bought it brand new and it's always been like that. But it's better to be safe then sorry, I've had an engine fire before and they're no fun lol!
  5. BRB46

    BRB46 Rockstar 100 Posts

    My son took it after I swapped out the alternator and in 20 miles it stayed at 13.2v and the chime didn't go off one time. So I guess it must have been the high voltage that it was warning me about.
  6. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    A fully charged lead acid battery cell should have a voltage reading of 2.1 volts, 6 of them in an automotive battery should read (at rest) 12.6 volts.

    A properly regulated alternator will out put a max voltage of 14.4 to 14.6 volts while charging; and it may drop to 13.2 while maintaining the charge.
  7. BRB46

    BRB46 Rockstar 100 Posts

    That's what I would have thought to be normal. The needle on volt meter always ran just above 14 and lately it was just about to the next mark up. I knew something wasn't right with it. Thanks for the info.
  8. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    does that truck have the variable voltage system? I can't remember what it is called. My 05 has a hall effect sensor around the negative cable. It is supposed to tell the pcm what demands for voltage are and adjust the alternator output accordingly. My voltage runs high driving in the city, but when I get on the highway it drops significantly.
  9. BRB46

    BRB46 Rockstar 100 Posts

    Well that's a good question. I guess I will look to see if I can find something out about that. Never heard of anything like that though.
  10. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    This is a long read, Just scroll to the bottom section: http://www.motor.com/article.asp?article_ID=1606

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