Do you have another battery you could swap just for a test?
I am thinking your battery is going bad and is giving funky voltage feedback to electrical system, another good thing to look at is all the grounds and make sure they are clean and good.

Here’s another item I just ran into on an 07 Silverado no start ( no crank) check all the fuses in fuse box under the hood, for continuity, pull them and check with meter.

on the 07 with no start issue, the fuse( 2A) for power from key to control modules was bad, it didn’t blow and to the eye it looked good.The aluminum had corroded internally and fuse would not complete the circuit, new fuse truck started right up.
These few items are easy no money checks.

 

I checked the IPC fuse, the battery is new and I did voltage checks with motor off and running and every thing passed test.
Thanks for your help.
Steve

 

Are you saying it was the fuse?

 

No, the fuse was OK

 

I have only run into two situations of this nature. The first one ended up being the alternator brushes and commutator were worn so badly that there was not enough spring pressure on the brushes to keep a good contact. The second was the electronic regulator internal to the alternator. Try this test, with the engine running and your 14+ volts showing, pull on the high beam headlights and air conditioning. You should see a momentary dip in voltage then a recovering to voltage that is very close to what the measurement was. If you don't see the dip or the recovery - the voltage regulator is no longer doing its job.

 

check ground number 103. It is back by the oil pressure sender unit on the back of the engine.It is the ground for the generator battery charging module. Just a thought.

The wire should be Blk/white tracer.