Voltmeter reading

[ukrkoz]

Will do.

 

[Geotrash]

Driving to work yesterday am, towards the last about 15 min of driving, noticed, that V meter needle dropped below 14. Connected Torque and is showed current oscillating between 12.7-13V.
OK, so panicking a bit, connect Torque on the way home - voltage sits at 14.7-15 across the entire commute, that being around 25-30 min. Gauge also shows as it should - above 14.
Is this about right, or I should just replace alternator? Or, it's voltage regulator acting up? Presuming, battery got charged, will voltage drop down not to overcharge it?

Perfectly normal. When the battery is fully charged, the alternator switches off.

 

[ukrkoz]

Yeah, not to jinx it, it's been all as it always was ever since. 14.7-15V.
Btw, if it bears any relevance. That fluke low reading was next day after I helped jump start some old monstrous diesel pickup truck with trailer, stuck in O'Reyley's parking lot. Amount of rusted wires, connected to battery on it was mind boggling. On 2nd try it all started smoking and I said - nope, we tried, sorry.

 

[Charlie207]

On Torque you can see the OBDII output voltage and system voltage (that the dash display shows). OBD port voltage almost always stays around 12-13v.

 

[Rocket Man]

Sounds like it’s the normal variable voltage regulator system in these. GM did that in order to lighten the load on the engine when the alternator isn’t needed, in order to increase gas mileage by a little bit.

 

[Doubeleive]

my experience has been even with the new RVC system is that when the voltage starts fluctuating a lot, or more than normal then the battery is getting weak even though it may pass testing. just my .02 I personally replace the battery at that point. It only takes once for me to get the hint as a dead battery can cause lost opportunity.
a small amount of fluctuation I consider normal, it's how the RVC system works.

 

[tom3]

Testing at GM showed around a 1 mpg increase when the voltage drops like this. There is a program that controls this, after fully sated charge it can drop for about an hour, then jump back up for several minutes to reactivate the battery charge. Or something like this. I've seen this on our 2019 quite a bit on the open road and we do get an average 22+ mpg on trips.

 

[Doubeleive]

Testing at GM showed around a 1 mpg increase when the voltage drops like this. There is a program that controls this, after fully sated charge it can drop for about an hour, then jump back up for several minutes to reactivate the battery charge. Or something like this. I've seen this on our 2019 quite a bit on the open road and we do get an average 22+ mpg on trips.

that is what the RVC system is designed to do, but it also does not take into consideration when the battery gets weak. a good fresh battery will result in little to almost no volt meter fluctuation, whereas a weak battery will have that gauge all over the place because the battery temperature throws the system out of whack. I had battery that would pass testing but would not hold a full charge anymore and it resulted in the RVC system not even working as designed at all, I could turn the wipers and seat heater and lights and radio and hvac full blast and still only get 11.xx volts because of the battery temperature.

 

[ukrkoz]

On Torque you can see the OBDII output voltage and system voltage (that the dash display shows). OBD port voltage almost always stays around 12-13v.

Both show normal voltage, maybe a tenth of volt difference

 

[Charlie207]

Both show normal voltage, maybe a tenth of volt difference

Mine will have the battery/alternator voltage around 14v, and the OBDII port around 12.5v.

I have a fairly new (Odessey) battery, and new 160amp alternator.

I do see the fluctuation on the dash gauge, and wondered (answered in previous posts) if there was a variable chargine system.