2014 Suburban Electrical gremlins

[bacon612]

Hello everyone. Just realized that this sub exists. I've been troubleshooting an electrical issue on my suburban where my radio cuts out, I have headlight and interior lights flickering as well as some unstable and high voltage.

Truck has 125k miles. Things I have done so far...
New battery
New OEM Delco alternator
New OEM negative battery wire (runs to cylinder head and lower rad support)
Cleaned grounds on lower rad support (right and left side)
Cleaned ground under drivers seat on frame
Replaced ground strap on left side of firewall to rear of engine block.
Added another ground from the same stud mentioned above (left side of firewall) to a bolt under the alternator mount.

I know that the voltage regulator on these trucks is computer controlled and varies based on a bunch of things but I am seeing voltage bounce from 14.4 to high 15s and as mentioned above, I have some flicker and my radio cuts occasionally. This to me indicates that I've got something going on.

Anyone have anything similar happening?

 

[Joseph Garcia]

There is a ground on the driver's side frame under the truck around the driver's seat location that many electrical items are tied into.

 

[bacon612]

So I undid that ground cleaned it up and reattached. No difference. I read that there's another ground on the frame rail under front passenger seat but don't see it.