1994 Ram 2500 4x4 auto

Never worked on a Chrysler alternator before. Did a little poking around and it appears that the two skinny screw terminals go to the field coil in the rotor, which shows 3 or 4 ohms with the truck turned off. When I turn the truck on, battery voltage appears at the bottom terminal. The upper terminal voltage varies, so it seems the computer controls field current from the upper terminal to ground (most likely PWM). But it doesn't really matter to me whether it uses linear or switch mode control. Just asking for feedback on whether I got the general scheme correct.

 

The PCM checks the battery temperature sensor, battery voltage and if the engine is running. It then supplies a DC voltage to the field terminals after looking up the value in its memory. No PWM or switch mode operation, just old fashioned linear DC control to the alternator.

 

From what I see, the computer ties one end of the field to the positive rail and controls the field current through the low end (the low end electrically speaking, not the lower of the two terminals).
And another thing, why the hell did they set it at 14 volts? Too low by at least half a volt.

 

Yes, the PCM uses a sink transistor to pull the field terminal down to increase alternator output.