2010 Denali-Intermittent voltage drop

[Tim907356]

When we bought the 2010 Yukon Denali, I noticed that occasionally, the voltage gauge would drop to below 13v. It quit doing that over the first month or so, and for the last several months, its always read above 14v.
I had to jump my mothers car this weekend, and since then, the voltmeter reads +14v when we start, but then it drops to ~12.5v (By the meter). When it’s off, it reads 12.35v. We’re getting ready to drive a couple of hours home, so we’ll be rolling the dice a bit!
So, is this an alternator, voltage regulator, both, or should I look elsewhere??
Thx for the help!!

 

[PG01]

Its normal, its called rvc... regulated voltage control.

basically stops the alternator from alternating (lol) when battery reaches full capacity, it turns it on and off, so to speak, When demands call for it. if you press tow/haul it will stay at say 14ish constant but will drop out of tow/haul when the computer see’s fit. Its another GM gas saver deal. If it sets your mind at ease, get a dvom or amy voltage meter and check voltage on tge battery with engine off, then start it up and see what alt is putting out at battery with the vm

 

[Tim907356]

Wow....I did not know that! I did meter 12.6v while running, and 12.35v when it was off. That did put my mind at ease; no way voltage would rise with load of the alternator wasn’t working..
Many thanks!!

 

[Doubeleive]

Wow....I did not know that! I did meter 12.6v while running, and 12.35v when it was off. That did put my mind at ease; no way voltage would rise with load of the alternator wasn’t working..
Many thanks!!

you should be getting more than 12.6 most of the time, when you start the engine each time it should automatically go up to 14+ at first then it will drop down a bit, you can check it also by turning on the rear defroster, windshield wipers on high, etc, the bcm controls it and put's it into "fuel economy mode" when you are just cruising with nothing else really running i.e. AC, seat heater, etc

 

[thompsoj22]

Its normal, its called rvc... regulated voltage control.

basically stops the alternator from alternating (lol) when battery reaches full capacity, it turns it on and off, so to speak, When demands call for it. if you press tow/haul it will stay at say 14ish constant but will drop out of tow/haul when the computer see’s fit. Its another GM gas saver deal. If it sets your mind at ease, get a dvom or amy voltage meter and check voltage on tge battery with engine off, then start it up and see what alt is putting out at battery with the vm

It does sense "load/voltage" and at highway speeds i dont even flynch when it drops the voltage as that is the design. The engineering flaw is that the module also senses temp, by system description the "battery temp" to avoid overcharging/overheating the battery.But what is actually happening is the module which is on the battery ground cable measures underhood temps, so when you are sitting in bumper to bumper traffic with the ac blasting the underhood temps soar and the module turns the alternator down? the rvc must communicate with the ECM which controls the alternator internal VR?

EDIT: there is a good GM tech explanation on the system. google RVC, and it will not turn down the voltage when ac fans are on high reguardless of temp which i stated above, im simply seeing the extreme load on the system pull down the voltage. i do install a 2 inch overdrive alt pulley in summer and it has cured this. the factory pulley is 2 3/8.

 

[BG1988]

When we bought the 2010 Yukon Denali, I noticed that occasionally, the voltage gauge would drop to below 13v. It quit doing that over the first month or so, and for the last several months, its always read above 14v.
I had to jump my mothers car this weekend, and since then, the voltmeter reads +14v when we start, but then it drops to ~12.5v (By the meter). When it’s off, it reads 12.35v. We’re getting ready to drive a couple of hours home, so we’ll be rolling the dice a bit!
So, is this an alternator, voltage regulator, both, or should I look elsewhere??
Thx for the help!!

dirty power cables i'd check them make sure they are clean

 

[OR VietVet]

Yes, like Brent said, I don't think there is a problem but if cables are original they should be checked at each end and make sure connections are clean and tight and also check for corrosion under the cable insulation near the ends of the cables. Would not hurt to crawl over the engine and check all grounds and under the vehicle front to back.

 

[Tim907356]

So here’s what happened on our ~2.5hr. trek. The voltage started at ~14.2 and climbed to 15v. After 1/2hr of highway, it dropped back to 13v over a 5 min period. It stayed ther for 1-2hr, then jumped back up to 15v.
This ‘cycle’ repeated itself regularly for the duration of the trip; 1/2hr at each voltage, followed by a slow transition to the other state. All values are interpreted by the dash gauge, so are approximate.
That doesn’t seem normal to me. We’ve had it for 4 months or so, and admittedly have not had any longer trips, but I don’t remember it bobbling around like that before, albeit repeatedly. It seems like it’s always been just over 14v.

 

[swathdiver]

So here’s what happened on our ~2.5hr. trek. The voltage started at ~14.2 and climbed to 15v. After 1/2hr of highway, it dropped back to 13v over a 5 min period. It stayed ther for 1-2hr, then jumped back up to 15v.
This ‘cycle’ repeated itself regularly for the duration of the trip; 1/2hr at each voltage, followed by a slow transition to the other state. All values are interpreted by the dash gauge, so are approximate.
That doesn’t seem normal to me. We’ve had it for 4 months or so, and admittedly have not had any longer trips, but I don’t remember it bobbling around like that before, albeit repeatedly. It seems like it’s always been just over 14v.

You're battery might be tired Tim. You can look for the date code on it to see how old it is. If it's a code per se, copy it down and then look it up on the internet.

If the TVs are on and or the kids have phones and stuff plugged in and it's hot out, that can really put a strain on the electrical system.

 

[iamdub]

While cruising steadily on a trip, a rhythmic pattern seems fairly normal to me. It charges as needed, then backs off and lets the battery run things for a while, then charges again when the battery gets to a certain point, etc.

I don't know how long I had mine before I noticed the voltage cycles. I unplugged the RVC sensor to have full-time charging but decided it was actually beneficial and plugged it back in after a couple months.