I have a 2006 3500 5.9 and the volt gauge at startup climbs very slowly to about 6 volts drops down to almost 0volts then starts to climb to 14 volts.Seems to be steady 14 after a few minutes. Is the alternator going bad or is it the grid heaters that suck that much power at startup.Was 40 degrees the last couple days here in upper michigan.Sorry but I just bought the truck a month ago and have been trying to learn as much as possible.Thanks in advance for the help.

 

clean all cables, check all connections and have batteries load tested. Sounds like you might need new batteries.

 

Thanks so much. Did have 2 weak batteries. Changed them out for 2 Interstate 1000 cold cranking amp batteries.Thanks for the help.