Alternator issue maybe???

[mikeyk101]

I went to start my truck today and only a couple chug, chug, chugs and no start. I kind of figured it might do that. I was out of town all week on a road trip on the motorcycle all this past week and it had sat the entire week before that as well. I had left my Range AFM disabler plugged in as well as a dash cam that is wired to have constant power for parking mode. So out comes the jump starter and I was able to get the engine to fire right away. Radio was on something like 87.3 FM and all static but presets were still at the bottom. 

 

However, the first issue was that I could not get Android Auto working at all. I kept getting a red screen on my phone telling me an error about security checks failed and to make sure that date and time was set on car radio. No matter what I did including deleting and then updating Android Auto several times would get it to work. I even tried restarting phone several times as well as turn ignition off and opening drivers door. Oh, well, I drive off and drove about 60 miles to where I was going, mostly highway. 

 

After getting done and starting to head back home, Android Auto starts working. Cool! After getting back on highway, I noticed that the voltage gauge was a bit low. I confirmed it with a digital gauge that's part of a multi USB hub I use plugged in the power port on dash. It is showing 12.5 volts. It stayed low for about 45 miles of highway driving then after getting off on side roads, it jumped up to middle on dash gauge and showed 13.9 volts on extra digital gauge. After a couple more miles, it went back down to 12.5 volts again and stayed there for rest of trip. 

 

Now on the gauge, it has a curved line at top with hash marks on either end and 14 right in the middle. My understanding from other threads is that the Silverado Alternators go up and down based on needed voltage but as long as it's somewhere inside the 2 hash marks, it's ok. The engine ran fine and showed no indication that it was being starved of power that usually comes up as an alternator fails and engine slowly drains the battery. It ran just as it always does.

 

Now the strange thing is that in over 87,000 miles, it has never gone that low and stayed there for any length of time. During winter, I have had it go up to 15.3 but it will usually be around 14.7 or so regularly, sometimes dropping down to 14.4 but never under. And I am kind of OCD about the gauges and constantly scan them throughout the drive and voltage is one that I have watched for many, many miles of driving. 

 

So why would it suddenly start working as it was designed now after never having done it in the past? And this is normal, correct?