Hello, have you checked the 7.5A alternator fuse in the fuse box under the hood.
I have a 3000 watt inverter installed and I assume it makes a lot more work for the alternator. I have replaced 3 alternators over the lifespan of this truck. (560K miles).
But every time the alternator has failed in the past, I have always gotten less than 13.5 volts at the battery with the engine running. The alternator seems to be still working as I'm getting 14.5. Do you think alternator failure is likely in the near future? I don't mind swapping out the alternator, but I'd rather not if the current one is still OK.
Sorry to hear that, the light is getting a ground somewhere, i was hoping through the alternator. The light get 12 volts applied to it when the key is on and the other side is grounded to keep the light on, when the engine is running 12 volts is applied from the other direction, this causes equal voltage to both sides turning the light off.
On the black connector on the alternator are three wires, one of them should be grey, this goes to the light and also to the body ecu. With the engine running and the connector connected backprobe the grey wire and check for voltage there, if there is no voltage check to see if the wire is grounding with the engine still running.
Take your time I'll be offline for about an hour.