What would cause intermittent power loss at the actuator valve? Is it just a bad selector on the dash or could it be something else. I have determined that the voltage when not working is 5 volts more or less at the vacuum actuator on the firewall.

 

The actuator valve, or solenoid, is operated by a switched ground in the Transfer Case Control Module. When energized, you should get 12+/- testing between both pins on the connector. When de energized, checking between the pins, you'll still see about 5 volts.
What are you trying to troubleshoot? It's not quite as simple as it sounds, what year and trim level is your truck?

 

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