It took 58 minutes for the game's first try, following a first half where Northland had most of the running but failed to capitalise.
While the first hour was a droning affair, the last 20 minutes had some spice, with a moment of magic from Northland winger Jordan Hyland snapping it out of a funk.
Hyland's scything individual effort saw him cut in from the right wing, beating three players on a 40 metre charge to the line, and finally saw the game shift out of first gear.
Harbour were quick to respond, and managed to nudge back into the lead when an overlap saw Tevita Li sent over in the left corner. While two penalties to Peter Breen restored Northland's buffer, Harbour had finally woken up.
As Northland tired, a try to Ben Volavola put Harbour in front, and they sealed the deal through a Matt Vaega intercept, to keep their unbeaten run alive.
North Harbour 31 (Li, Volavola, Vaega tries, Gatland 2 cons, 4 pens)
Northland 22 (Hyland try; Breen con, 2 pens, Hawkins 3 pens)
HT: 9-9