M998 charging issue?

[trooper632]

Got the Generator fixed and installed it, gauge showed it working/Charging. A couple of days later the gauge wont get out of the yellow, so my question is can I check it some how to see if its the gauge not working or if its truly the Generator not charging. Can I check it without taking the Gen out again?

 

[DatGuyC]

Volt meter across the batteries while it's running, 24v or less means it's not charging. Should have 28v when it is.