I have a 99 dodge with a Cummins. During a winter snow storm, the truck
experienced an unusual problem. The charging rate  (on the amp meter) jumped
to about 16 volts. This caused the head lights to brighten and the air bag
light and chime went off.  This problem would cycle on and off
inconsistently. Once the air temperature was back to normal the trouble
disappeared. The dealer could find nothing except that there was a record of
an overcharging.  I thought it was related to cold and wet conditions until
late Friday when it happened again. However, there was nothing related to
cold and wet. The problem is definitely inconsistent. This morning on the
short drive to the dealer, the amp meter jumped to over charge position
twice and the air bag light and chime went off. The moment I arrived at the
dealers lot, the charging rate returned to normal. They have never had such
a problem. My guess is it is related to whatever controls the charging. I
replaced the batteries after the first trouble, however, obviously that was
not the problem.
Has anyone had such a problem. Any suggestion on what module that I should
consider replacing?
Anyone have any idea how the charging system works as there is not voltage
regulator. Is there a relay somewhere. The dealer seems at a loss. any
thoughts would be appreciated.