2004 f150 4x4

Today while driving, my battery light came on reading high (and my glowshift gauge read 16v). I started hearing a hissing sound like a vacuum leak coming from engine, then I heard what I believe were my actuators trying to engage. Shortly after I heard a clunk in the front end and then everything went back to normal. I turned on 4HI and nothing, no light, and I could not feel that the actuators had engaged. I turned off 4HI and drove for a few hundred yards then turned it back on again and the light came on the actuators engaged and it worked fine.

I just replaced the actuators 2 weeks ago and tested them and everything worked fine. I checked all the vacuum lines beforehand and found one clogged, so I cleaned it out and made sure the check valves were ok and the reservoir was ok. I tested vacuum on all the lines and they all held vacuum without leaking down. Vacuum from the intake was around 21. The solenoid was replaced about 3 years ago and still works.

Any one experience this and how does a high voltage tie in to all this?
I started experiencing high voltages about a year ago. I replaced the battery and alternator and it didn't get rid of the high voltages. The high readings are rare and I have only seen the battery light come on about 5 times in the last year. 99% of the time it runs around 14.2-14.4v. There are no other symptoms or issues that occur with this battery voltage spike.