08 Silverado Fluctuating volt gauge............. Again

Ok I need to revisit this issue with my truck that I though I had cured after I replaced the old negative battery cable with a new one.The truck is an 08 Silverado LT 5.3L 4x4 crew cab.Earlier this summer I had issues with the volt gauge fluctuating from charge to discharge and thought I had it fixed but today while on my way home from a mini vacation I noticed the gauge showing what I am guessing to be about 12.5 volts or so,down from the normal 14-14.5,and being that I had about 300 miles to drive the last thing I wanted was to have to turn around and find a garage or parts store to buy a new alternator or battery.I continued driving and after about 20 miles or so the gauge came back up to normal and stayed there for about 5 miles,give or take,then it dropped again.I stopped and fueled up,pulled back out onto the highway and the gauge was normal for a few miles then dropped to about 12.5 ish.I never bothered to check anything under the hood,I just kept driving to see what would happen and this happened the whole way home,every so often the charge rate would be normal then drop off.It was explained in my older thread that the sensor on the negative cable was supposed to alter the current draw from the alternator depending on the charge of the battery,what I need to know is would the fluctuating gauge be the result of this sensor?This is the first time I have ever driven my truck this many miles all at once,it has always been 30 here 50 there kind of thing and the volt gauge always showed it's normal 14-14.5 vdc so is this kind of thing normal or should I be looking at the possibility of changing the alternator?

http://www.justanswer.com/chevy/6u8az-chevrolet-silverado-1500-does-charging-system-work.html

Some info for you.

Hmm well that is some interesting reading there,thanks.One thing I will try the next time I see the gauge doing what it was before is click the tow/haul button to see if the gauge springs back up.

I see that running the wipers is supposed to put the charging system back in full mode but I wonder if using the pulse feature of the wipers is supposed to do this too because at times I was using the wipers in pulse mode but the gauge still showed low.

Hmm well that is some interesting reading there,thanks.One thing I will try the next time I see the gauge doing what it was before is click the tow/haul button to see if the gauge springs back up.

I see that running the wipers is supposed to put the charging system back in full mode but I wonder if using the pulse feature of the wipers is supposed to do this too because at times I was using the wipers in pulse mode but the gauge still showed low.

with short trip driving this system will not drop the alternator output. this is because the battery charge state will be low. when driving on the hywy for a time this will charge the battery to a full amount then this system begins to turn off alternator and then back on... when you see,,, this turn on the rear defrosters. if the voltage comes up then you know it is this MPG saving system at work ...MPG saving is what GM says...battery killer IMO...