I have a 99 ram 3500 with a very unstable charging system.it goes from not charging to over charging. You can see the flutter in all of the lights

 

Normal. Grid heater is cycling.

 

grid heater cycle even when engine is at 190 degrees?

 

If the outside temp is below 45, the grid heater will cycle.

 

i bet it go's away when ya rev the truck up

 

for the most part yes it does

 

yeah the headlights will be dim at idle but get brighter as revs come up also and at the same time the alt meter will come up to normal

 

Huh didn't know the grid heater would cause that..... learn something new every day. My first thought was that it would be the regulator.

 

Okay, Not to but in, BUT Most likely you are loosing charge if it's occuring over 190 simply because the IAT would have cut the grid heater off by then. There again, Very common problem we see is a bad ground at the PCM , Incorrect IAT Reading or Damaged PCM. The truck should charge around 13-14 volts REGARDLESS of RPM based only on the PCM's Controls is the alternator switched on or off. The first place to check is the voltage it's really producing. If you want to confirm a grid heater/Amp/Volt issue, just unhook the grid. These trucks alternators are PCM Regulated.