I have the National Luna with the sensor. Mine doesn't always go off and can't explain other than it appears to be when I let the truck sit for a while. On startup the alternator will surge for a few minutes to quickly charge up the battery. If it goes off after a few minutes I wouldn't worry about it. Mine doesn't go off for 5 minutes by any stretch. Maybe 30 seconds or so when I first crank up. As Dave mentioned almost 15v is a little excessive. Is that what your reading or just a guesstimate?
97 Crusher, Slee'd 6 inches, All 3 Factory Diff locks, Hanna Sliders, Slee F&R Rock Crushers, M12000 Oops, I did it again saver -- SuperCharged.......0-60 in 5 seconds,
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What Did the Five Fingers Say to the Face.....