The drop is normal I researched this years ago when I first noticed it and it surfaced again last week at nationals as Trey mentioned. him and I researched it again. the odd thing here is many people don't ever look at the voltmeter that often and don't notice the fluctuation, but watch it closely if they think there is an issue. it was about a year after I bought my 08 when I noticed it for the first time after starting audio system upgrades and did some research on it. Mine drops down and stay down for extended periods of time, regardless of accessory operation. there are however 2 ways to force the system out of this lower voltage operative state. switching into tow mode and turning on the headlights.
Below is an except from a TSB issued regarding this condition (this was issued in 2011, but I assume it continues through the 2013 model year)
Below that is a photo of my voltmeter I specifically took to send to Trey. This was where the needle was for about 6 of the nearly 10 hour drive home on Sunday in high 90 degree heat. I had had my programmer plugged in most of the way just to monitor it more closely after the discussion regarding it on Saturday and at no time was the system outside of normal operational range. I would suspect what you are experiencing is totally normal.
"Models: 2005-2011 Cadillac Escalade Models
2005-2011 Chevrolet Avalanche, Silverado, Silverado Classic, Suburban, Tahoe
2005-2011 GMC Sierra, Sierra Classic, Yukon Models
Voltmeter Fluctuation Condition:
Some customers may comment that the voltmeter is fluctuating between 11 and 14.5 volts on their full size pickup or utility vehicle. Starting with the 2005 model year, light duty full size pickups and utilities are equipped with a new Regulated Voltage Control (RVC) system. This system reduces the targeted output of the generator to 11.8-13.1 volts when in "Economy Mode" to improve fuel economy and prolong charging system performance and longevity. The generator may exit "Economy Mode" if additional voltage is required. This will cause the voltmeter to fluctuate between 11.8 and 14.5 volts as opposed to non-regulated systems that usually maintain a more consistent reading of 14-14.4 volts. This fluctuation with the RVC system is normal system operation and NO repairs should be attempted.
Camper/Trailer Battery Charging Concerns:
Some customers may comment that when towing or hauling a camper/trailer, the auxiliary battery for the camper/trailer will not stay charged. In most cases, this concern is blamed on the new RVC system. While the RVC system does reduce the generator's targeted output voltage to 11.8-13.1 volts when in "Economy Mode", this feature is bypassed if the tow/haul feature is enabled. With the tow/haul feature enabled, the RVC system will stay in "Charge Mode" and the targeted generator output voltage will be 13.9-15.5 volts, depending on the battery state of charge and the estimated battery temperature. To keep the generator in the "Charge Mode", use either of the following two methods.
? The first method is to use the tow/haul mode when towing or hauling a camper or trailer.
? The second method is to turn on the headlights, which will increase the generator's targeted output voltage to 13.9-14.5 volts."