Capacitor always on?

azn, are these voltages measured at idle?

13.8 - 14 is normal for most late model vehicles when running so I would not be too concerned. however on older vehicles I have seen cases where the voltage measurments do not increase very much when running vs. not running, but the vehicle still functions and starts as well as any other.

You state your friends is 14.4. Is the reading from the same DMM?  Are both your explorers the same year and same options?

In my reference to "higher power alternators" I am speaking about a replacement alternator in vehicles where we are using amplifiers that demand current which exceeds the stock alternators rated output. I have noticed that when I take voltage reading at idle, the reading is actually lower then what I read from the stock alternator. Once you bring the rpms up, thats when I get the higher readings.

The thing that I question is this "lag" . You state it happens when you turn on the fan. Mad scientists also mentions this as 'momentaty dim" when condenser fans, defrost is used. Also mentioned is AC compressor. I notice that ac compressors can lower engine rpm (drag) and perhaps that is part of the issue. However most systems also raise the rpm to compensate but I imagine there is a time lag between when the compressor is turned on, to raising the rpm. regardless, the electric blower fan will turn on with the compressor if the HVAC was off to begin with.

I know that electric motors when first turned on basically can act as a short circuit, or very close to it for an instant which is why many vehicles use breakers for things like power windows etc. Now I am wondering since this is the case that perhaps when the motors are first powered up, if the very low resistance when the motor is initially activated is causing a current draw that is exceeding the alternators output for a brief lenght of time. Perhaps even more then the battery can deal with. But once the motors are running I would think the voltage would stabilize not so much by the alternator "kicking in" but as a result of the current draw decreasing once any electric motors are operating. And maybe this 'lag" is simply the amount of time the charging system/battery takes to stabilize. Additional draw is on the wires as well during this period so there may be a few factors that come into play.

Keep in mind this is only a theory and there may be more to this.