Charging question for Chevy Mechanic.

[Flyinfool]

I have a 2011 Silverado LT, 5.3L.

When I first start the truck it is charging at 14.8 - 15.0 Volts. After a while it will instantly drop to 12.6 - 12.8 V. While driving it is either at the high or the low volts, It never runs in the middle at 13.8-14.0 like everything else I have ever owned. I was told that the computer plays some games with the alternator on these trucks.

Is this High and low charge voltage normal?

I am not basing this on the dash gage. I am using a good Fluke meter.

 

I still need to buy a factory shop manual for this truck.

[Eck]

It is normal on these trucks.

I had a 2000 Silverado and it did same thing.

I now own TWO Avalanches (2005 & 2011) and both do same thing.

I just drive them..

[Flyinfool]

As long as it is supposed to do that I can deal with it, I just want to be sure that if there is a problem, I get it fixed while it is still under warranty.

[Guest tx2sturgis]

It's broke, you should sell it to me for $100.

 

[Flyinfool]

I could never allow a broken anything to be dumped on someone else. I guess I am stuck with it till it is fixed in another 250K miles or so.

[GeorgeS]

If battery is staying charged, and everything works, don't think its a problem.

[Flyinfool]

I was just trying to head off a problem before it becomes a real problem.

After reading up on a copy of some pages from the service manual, this is weird operation is normal and the way it is supposed to work.

When cruising down the road the computer will occasionally turn off the alternator to help save fuel. The computer will also kick it way up at other times and under certain conditions. this all lines up with what I was seeing.

[naturbar]

"When cruising down the road the computer will occasionally turn off the alternator to help save fuel." so in theory gas mileage decreases if the headlights or any aux. device is being used (due to increased load on alternator). it would be interesting to know how much fuel could possibly be saved over the course of vehicle ownership. somehow i believe the the savings would be insignificant - just my two cents :-)

[Flyinfool]

On my old truck I did notice about a 2 mpg drop in gas mileage when I had all 400 watts of lights on compared to running in daylight with no lights on. You could even hear and see the engine rpm drop when you turn on the lights.

It does take power to make power. Power comes from the gas tank.

I can see about the same 1-2 mpg difference with the instant MPG readout when I turn on all of the lights on this truck. That is a 5-10% difference, that is enough to save about 1 gallon per 1,000 miles. It takes a lot of little things to add up to make a decent savings. That is why I turn off the daytime running lights, its just one more little thing to save on.