Ok, maybe this is normal - just seems a bit different.
This moring it seemed like the voltmeter was slow to come up, caused the check engine light to stay on a second or two longer.

Under load the voltmeter is reading a half needle above 14 volts; I don't remeber what it read before, but thought it might have been more.
With the motor off it reads 12 volts - start the motor and the gauge 'slowly' climbs to 14 volts (about the same speed the oil pressure gauge rises)

All else seems fine.
Is this normal?
Am I remembering things differently?
Is this a 'sign' of potential alternator trouble?
Time for a beer and shut-up?

 

Cold temps work the grid heaters more. Normal.

Plug it in below 40F.

Your batteries maybe getting weak. If they are 12.4 volts or less after resting 8 hours they may need to be desulfated. Look into getting a Battery Minder Plus. It breaks up sulfated batteries and restores them to new.

https://www.dieseltruckresource.com/...battery+minder

Get a beer and keep asking good questions.