One of my friends has a 98.5 dodge cummins and when he very first starts his truck up the volts are low buy when he drives it about 10 minutes the volts are normal what could this be? Batteries or Alternator? possibly?

 

Maybe have a read over this thread:
https://www.dieselbombers.com/24-val...batteries.html

 

grid heater

 

Grid heaters pull up to 200 amps at a time, and cycle after the engine is run. If he notices the lights dim, engine grunt a little, that's the grid heaters running.

 

ya its normal grid heater sucks alot of juice takes time to recover after start up

 

could be the pcm,voltage reulator runs thue computer,my 02,sometimes has same systems even w/new alternator,battery cables,optima red top batts.i did work on a 98 earlyer this year truck had simalar symtems and it was the pcm,i would fully charge batteries and load test em,clean cables and grounds,hope this helps,have a great turkey day!!!!