14.8 volts normal ?

alternator with remote sense stabilize voltage on batteries compensating voltage drop on long wires (about 1V).

So check voltage on third wire, it runs from battery box directly. Inside the alternator there is small resistor (150 OHM) that connects voltage regulator input with B+ terminal. If RS wire is broken is stabilizers voltage by B+ terminal.

ECMs are designed for US and EU use so they work from 10 to 33V, but not all. ABS, EBS, ECAS and some dashboards work with 8-16V supply. Over 16V may damage them

 

my 379 has always set just on the green side of te divider between red and my dads 379 sits a 15 been like that for 4 years and hasn't hurt anything to my knowledge yet

 

yep, only way is to tilt cab

 

Napa is a "business," not a type of battery. Go get your receipt and find out what "KIND" of battery you have. If it's a lead-acid battery then 13.8 Vdc is the normal cell voltage. AGM glass-mat batteries have a different battery chemistry, and the normal cell voltage for those kinds of batteries is 14.5 Vdc.

You see what I'm getting at? If you have that different KIND of battery, the voltage you're seeing is normal.

 

AGMs are one of two types of sealed maintenance free batteries and 14.5- 15.4V is considered normal. Most people tend to go for the cheaper ones.

 

Usually AGM are not supplied here, in East Europe, becouse it is cold every winter and AGM fails with low temperatures. But ultracapasitors really work

 

That's nice. The OP is based in the United States.

 

International COE.... batteries as I remember are located behind cab, easy to access and check voltage on terminals with AVOmeter

 

Just replaced my Delco Remy 36SI 170 Amp , old one ran 13.8 - 14.1. This new one now runs 14.1 - 14.5 . Contacted the OEM and was told that is the normal operating range on these now.