i have a 2004 2500 ram quad cab 4X4 CTD. at startup I notice sometimes (especially first start of day) that the voltmeter reads normally low(12ish) while idling. Until I start driving or something it moves to normal or (around 14 volts). Then it hangs at 14 or 14.5 all day long.(which is good). Why does it go low at the start ? does it need to be excited like the old alternators or something?

 

Well if it was an 06 I would tell you it was the grid heater cycling but on an 04 I am not sure but it most likely is the same thing. The heater will cycle a few times during the first 2 minutes of operation and the voltage will drop and the lights will dim.

 

It's the intake air heater. It cycles on and off during cold idle, and will stop when your truck reaches 18mph. It tells you all about it in your owner's manual. That's the first thing I read when I get a new vehicle. Does nobody else?

 

Well it reads "12ish" because it is a 12v system, however when it reads up to 14-14.5 that is because the alternator has now caught up and is putting out a few higher volts to keep up with accessories so the lights don't dim and to keep the battery charged.

 

I read the oweners manual the same night, usually cover to cover skipping the obvious.