# Voltmeter in car acting up **URL:** \ **Category:** General Discussion\ **Tags:** acadia, gmc\ **Created:** [July 17, 2021, 10:44pm UTC](https://community.cartalk.com/t/voltmeter-in-car-acting-up/178104 "2021-07-17T22:44:14Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [July 17, 2021, 10:44pm UTC](https://community.cartalk.com/t/voltmeter-in-car-acting-up/178104/1 "2021-07-17T22:44:15Z")
So on our trek to the cabins the voltmeter descended to 13 volts and stayed there. At a stoplight it crept back up again then driving speeds crept back gown again. Restarted after filling with gas, was fine but driving away it crept down to again. Drive through in gear crept back up again, on the highway crept back down.Starts creeping down before going into overdrive. Coasting in neutral, no change. Got to our destination reading was 13. Stopped and restarted the engine, normal. 2017 Acadia limited 3.6 vvt, 30k miles… I suppose a voltage display for the power point step 1 ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [July 17, 2021, 10:52pm UTC](https://community.cartalk.com/t/voltmeter-in-car-acting-up/178104/2 "2021-07-17T22:52:17Z")
My first test if I had that problem, I’d use a DVM to verify the dashboard display matches a direct DVM measurement on the battery. If the DVM matches the dashboard display, second is a battery test, esp if the battery is over 4 years old. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [July 17, 2021, 11:35pm UTC](https://community.cartalk.com/t/voltmeter-in-car-acting-up/178104/3 "2021-07-17T23:35:50Z")
Battery was replaced, Jan or so ignition off as in engine not running reading is this hard to figure voltage for me… No dvm at the moment. ![batt](https://global.discourse-cdn.com/cartalk/original/3X/5/b/5b96dc72ae660ca1c311c1f8977895b313a5a905.jpeg) ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [July 17, 2021, 11:41pm UTC](https://community.cartalk.com/t/voltmeter-in-car-acting-up/178104/4 "2021-07-17T23:41:36Z")
I understand completely. You’d think the marks would be either 1 volt or 1/2 volt increments. But those marks on your dashboard have little to no relationship to any sort of voltage scale I’ve ever seen … lol … about all I can say is best of luck. ---
**Author:** ![Renegade](https://avatars.discourse-cdn.com/v4/letter/r/b4bc9f/32.png) [@Renegade](https://community.cartalk.com/u/Renegade)\ **Post date:** [July 17, 2021, 11:48pm UTC](https://community.cartalk.com/t/voltmeter-in-car-acting-up/178104/5 "2021-07-17T23:48:24Z")
At least you can get some sort of Idea of what is going on compared to one with a idiot light with no gauge. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [July 17, 2021, 11:50pm UTC](https://community.cartalk.com/t/voltmeter-in-car-acting-up/178104/6 "2021-07-17T23:50:48Z")
No idiot lights went off! ---
**Author:** ![Renegade](https://avatars.discourse-cdn.com/v4/letter/r/b4bc9f/32.png) [@Renegade](https://community.cartalk.com/u/Renegade)\ **Post date:** [July 17, 2021, 11:54pm UTC](https://community.cartalk.com/t/voltmeter-in-car-acting-up/178104/7 "2021-07-17T23:54:29Z")
What I meant was one like my wife’s car the only gauge it has is the fuel gauge. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [July 17, 2021, 11:55pm UTC](https://community.cartalk.com/t/voltmeter-in-car-acting-up/178104/8 "2021-07-17T23:55:07Z")
I hear you! ---
**Author:** ![circuitsmith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/circuitsmith/32/40376_2.png) [@circuitsmith](https://community.cartalk.com/u/circuitsmith)\ **Post date:** [July 18, 2021, 12:32pm UTC](https://community.cartalk.com/t/voltmeter-in-car-acting-up/178104/9 "2021-07-18T12:32:00Z")
Is this new behavior? It might be a “smart” charging system that reduces voltage to save gas. That’s what my 2017 Tucson does. Sometimes voltage drops to 12.6V. More about it here: > [@Overriding a "smart" battery management system](https://community.cartalk.com/t/overriding-a-smart-battery-management-system/171538): > > Like many modern cars the Tucson reduces battery voltage when it decides the battery is charged “well enough”. It does this to mainly save a little fuel and also avoid over charging the battery. I have a voltmeter plugged into a 12V port so I can monitor system voltage while driving. When the battery is full (or nearly full) system voltage drops to 12.6V, with 4 exceptions. When steady cruising it raises the voltage to 13.x or 14.x (varies with temperature) volts for a few minutes every ho… You can get one of these for comparison: [https://www.amazon.com/gp/product/B01M9IKYVH](https://www.amazon.com/gp/product/B01M9IKYVH) ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [July 18, 2021, 2:39pm UTC](https://community.cartalk.com/t/voltmeter-in-car-acting-up/178104/10 "2021-07-18T14:39:25Z")
Interesting thought. 'll check with the dealer. I can certainly hope it is by design. I’ll check with the dealer Monday! ---
**Author:** ![asemaster](https://avatars.discourse-cdn.com/v4/letter/a/5f9b8f/32.png) [@asemaster](https://community.cartalk.com/u/asemaster)\ **Post date:** [July 18, 2021, 3:53pm UTC](https://community.cartalk.com/t/voltmeter-in-car-acting-up/178104/11 "2021-07-18T15:53:32Z")
Sounds perfectly normal. Modern day GM cars with AGM batteries control charging output to maintain the battery efficiently. AGMs don’t like or need a constant 14.4 volts when the engine is running. Can you toggle through your Driver Info Center display to have it display system voltage? My wife drives a 2018 Cadillac and I can be driving down the highway at 70mph and see the system voltage go to 12.4 volts for periods of time. ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [July 18, 2021, 6:38pm UTC](https://community.cartalk.com/t/voltmeter-in-car-acting-up/178104/12 "2021-07-18T18:38:55Z")
Adaptive charging systems have been around since the 1980’s. Charge the battery at 15 volts after start up on a very cold day, 13.0 volts on a hot day. Charging close to 12.6 volts is best for the battery, charging at 14.5 volts on a 12 hour trip will age the battery faster. A decade ago manufactures began using extreme measures to save fuel, reduce charging voltage to minimum while accelerating or cruising, then increasing voltage while deaccelerating to capture some of the energy wasted while braking. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [July 19, 2021, 7:48pm UTC](https://community.cartalk.com/t/voltmeter-in-car-acting-up/178104/13 "2021-07-19T19:48:24Z")
Dealer confirmed all is normal, surprising it never happened before, maybe it kicked in as the new battery in Jan. required programming to keep auto start working. My regular guy was saying he had to buy the battery from the dealer then program it, figured might just as well let the dealer do it, downside 630 cca. First long road trip since then. Blood pressure down, life is good!