Those selectable gizmos have two low-drop-out (LDO) voltage regulators in them rated at 5 amps capacity each. One of them is a 5 volts regulator, non-adjustable output. The other is adjustable from about 1.8 volts output up to nominal charging system voltage, minus the drop-out voltage and circuit losses, so roughly about 1.8 volts up to 14 volts on the bike.
The first regulator supplies 5 volts continuosly to the OEM throttle housing 2wd/4wd switch while the key is on, which trips a PCB mount 5 volt relay (a 5V - 40 milli-amp load through that switch guarantees that it will last for decades) that sends battery voltage to the adjustable regulator when 4wd is selected.
I settled on adjusting the supply voltage for the selectable front diff clutch coil gizmo to 9 volts, after testing that clutch using 4.5 volts up to battery voltage. The clutch worked fine even at 4.5 volts... it was sure and strong on engagement, so I did the math to help guide me to a reasonable decision. This is a snippet I posted in the Creamsicle thread:
This spec for the clutch coil came from the 400AT FSM:
Clutch resistance: 5.1 - 5.8 ohms (68 degrees F)
This link can be used to predict gross clutch coil currents and power consumption at various coil voltages, using worst-case coil resistance of 5.1 ohms, for comparison purposes:
Watts/Volts/Amps/Ohms conversion calculator
Predicted results (rounded off):
At 14.5 volts unregulated battery voltage the coil power/energy consumption = 41.22 watts - 2.84 amps
At 12 volts = 28.23 watts - 2.35 amps
At 11 volts = 23.7 watts - 2.15 amps
At 10 volts = 19.6 watts - 1.96 amps
At 9 volts = 15.88 watts - 1.76 amps
At 8 volts = 12.54 watts - 1.56 amps
At 7 volts = 9.6 watts - 1.37 amps
At 6 volts = 7.05 watts - 1.17 amps
At 5 volts = 4.9 watts - 0.98 amps
So adjusting down to 9 volts through that clutch coil prevents it from building heat needlessly... we cut the wattage by more than half (comparing to charging system 14.5 volts) while trimming the current by just over 1 amp. The clutch coil voltage is fully adjustable via a trimpot at any time on the bike though (depress a momentary switch and coil voltage displays on the voltmeter), if the user decides to adjust it to some other voltage.
A cheaper and much quicker, simpler solution might be to run battery voltage through the selectable switch which trips a 12 volt relay, which supplies battery voltage with up to the full 2.84 amps of current through the clutch coil. I have no idea how long that simple setup might last though. Plus e don't get to drop stuff and break stuff with our old, fumbly fingers.