Forum Discussion

1ed's avatar
1ed
Explorer
Mar 09, 2020

Help Me Understand

I have a 2013 Chevy Silverado Extended Cab with 5.3 engine with 77000 miles on it. I purchase this vehicle in April 2019.
I have driven it about 2000 miles and pulled my 23 trailer with no problems.
However, this Friday I noticed the Voltmeter was under 14 on the gauge and thought I might be having a alternator problem. After driving a couple of miles uo the road the gauge returned to plus 14. I did not change anything on the vehicle and it returned to what I consider normal or 14. I had a trip planned and since this is the first I have noticed this I thought It was better to cancel the trip until I determined exactly what if any was the problem. I put in a new interstate battery in November 2019. When i got home I checked the battery and it was 12.8 checked the alternator and it was 15.8. I let the truck sit for a few hours and checked the battery and it was still 12.8 checked the alternator and it was 15.8
Got the owners manual out and did not find anything that was informative on my situation.
Google different topic and found out on the SilveradoSirream.com web site that this is normal do to the economy mode system on the truck which has to do with the Fuel Magament System.

DOES ANYONE HAS A SITUATION WHERE THE VOLT GUAGE FLUCTUATES BETWEEN THE ONE ON THE 14 AND PLUS 14 ON THE GUAGE.

I Will be called the dealer in the am tomorrow. Thanks Ed
  • DrewE's avatar
    DrewE
    Explorer II
    Mar 09, 2020
    Nothing sounds out of the ordinary to me. The voltage will fluctuate based on the electrical needs of the vehicle at the moment, the state of battery charge, and what the electronics in the vehicle computer think is appropriate charging for the conditions. On many modern vehicles it does cycle the alternator under low load conditions once the battery is charged to help save fuel. Even without that, changes in electrical loads are entirely possible, such as from automatic headlights turning on or the radiator fan starting up or stopping. Your battery is getting charged while you're driving, clearly, so the system sure seems to be working as designed.

    (I don't have a GM truck, but I certainly have noticed the voltage varying on my Honda Fit for various reasons while driving, and its charge system empirically has worked just fine in as much as the small original battery is still installed and working after 7.5 years and over 150K miles....)
  • MEXICOWANDERER's avatar
    MEXICOWANDERER
    Explorer
    Mar 09, 2020
    15.8 is to high for a CS144 Delco alternator. Love to. Help but impossible on this cell phone. Sorry.
  • MitchF150's avatar
    MitchF150
    Explorer III
    Mar 09, 2020
    That's what a gauge is supposed to do.. Unlike the Ford ones which just sit at one position and is nothing more than a warning light..

    Wish my gauges actually moved....

    You are fine.. I think what you are saying is why Ford went to the non moving gauges...

    Like I said, I wish my gauges actually moved..

    Mitch
  • owenssailor's avatar
    owenssailor
    Explorer
    Mar 09, 2020
    The GM trucks have a process to cut the field current in the alternator so they don't charge when the battery is full up and there is no other loads. This improves fleet fuel economy ratings. Nothing wrong. There was a tech bulletin on this.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Mar 09, 2020
    14 is actually a tad high... But GM does like to run the system on the high side.. I will alarm one monitor I have at that voltage (I silenced he alarm the hard way) But based on your post I'd not worry. Sounds normal for a GM.
  • joebedford's avatar
    joebedford
    Nomad II
    Mar 09, 2020
    I have a 2011 Silverado with a Duramax. It starts at 12V and quickly (20 seconds) rises to 14V where it stays no matter what is going on. Original batteries.

    My Harley OTOH would start at 12 and go to 17 and higher as revs went up. It was a fried voltage regulator. Replaced it and the battery as it was probably damaged from over-charging.
  • theoldwizard1's avatar
    theoldwizard1
    Explorer II
    Mar 09, 2020
    First, most dash mounted gauges are not very accurate.

    Second, unlike older (pre-2000) vehicle, modern vehicles vary the charging voltage "as required". Using a "good quality" meter and measuring directly at the battery posts, typically the voltage will be above 14V shortly after starting, but will drop down to around 13.8V after it has been running for awhile.

    If it drops below 13.2V at "fast idle", you have a problem !
  • Mike_LeClair's avatar
    Mike_LeClair
    Explorer
    Mar 09, 2020
    Yup, I believe that GM uses the acronym "RCS" for Regulated Charge System" or somehthing along those lines. My 2006 Sierra 3500 does pretty much the same thing except I don't think that I have ever seen it as high as you are noting. I have seen it hit 15V under heavy operating load.

    Cheers!

    Mike
  • ScottG's avatar
    ScottG
    Nomad
    Mar 09, 2020
    14 is totally normal in a modern vehicle. If it's very cold it will be even higher than that and if it's hot, it will be lower.
    No worries.

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