[JerryPSD]

i noticed about a week ago on a road trip that my 97 F350 was running at about 9-10 volts (needle right at "N" on the "normal" below the gauge). during the 4 hr trip the voltage came back up to 12-13. i had my laptop plugged in, lights on, trailer lights lit up etc.... ever since then the gauge has sat on N (9ish volts) i've never had this voltage problem before but it is normal for my voltage gauge to pulse between about 9 and 12 when i first start the truck. is it possible that the glowplug relay is stuck in position that is causing a constant draw??? truck has no problem starting.

truck has newish alternator and odyssy batteries

 

[Excavator]

My bet is that nothing at all is wrong except that the gauge is bad. Next time driving tap the gauge with your finger hard and watch it come back up. Now to be sure just hook volt meter to back of alternator and see what it is putting out.