One item on the Kenworth dealership service records mentioned an issue with a low voltage light. Their solution was to replace the belt on the alternator and charge the batteries. On the trip home I noticed the battery icon would appear once in a while. It seemed odd since the voltage display was always 13.8-13.9 volts and the alternator appeared to be brand new.
After having looked at the Volvo electrical schematic and the Delco documentation I noticed a couple issues. Someone had connected a wire between the batteries and the 'R' terminal on the alternator. My assumption is someone thought the 'R' was for 'remote sense'. It's not. I removed that wire. Above the output terminal in the alternator pictured is a knockout where an optional 'S' terminal would be. That is for 'sense'.
The electrical schematic showed a wire labelled '14' connected to the 'I' terminal on the alternator. The 'I' terminal is often used for the battery light. This wire was connected to the battery output terminal so I moved it to the 'I' terminal.
I've not had any issues with the low voltage light since making those changes.