I was driving truck no 1 (in signature) yesterday on a very cold morning when the GEN light came on below the tachometer. I then noticed that the voltage meter needle was only at the first bar, well below the middle bar marlet '14' volts. This leads me to preliminarily conclude that my alternator is not charging.

Any thoughts?

 

Hi,

Yes I would agree but this happens alot when first starting my truck then after about 30 secs it jumps to about 14V, the air heater cycles as you are likely aware. Prudent to verify no charge as you will be left with dead batteries in a short time.

Clean and tighten battery posts would be my 1st move.
Goodluck

 

I have never had the grid heaters pull it down to where the Gen light came on, but I also don't let my terminals get corroded. Check the connections well, then you might be looking at the Alternator.
How many miles on it?