Harbour were playing their second game in four days and seeking their first win of the campaign after consecutive losses to Auckland (20-27), Counties-Manukau (14-44) and Wellington (27-35). But they were buoyed by their second half fightback in the capital and the return of captain and hooker James Parsons.
It was tied at 8-all after the first quarter. Blindside flanker Jordan Manihera finished off 16 phases with a try in the corner for Harbour but Northland struck back almost immediately when Rene Ranger turned over possession and wing Rupeni Caucaunibuca raced 60m for the try.
It got even better for Northland a few minutes later when fullback Whiria Meltzer finished off a 70m move which featured some brilliant support play. Caucaunibuca scored his second after 34 minutes, barging through a tackle after he received the ball on the bounce from an attacking scrum.
That gave Northland a 17-point lead at halftime, an indication of their strikepower out wide despite the earnest endeavours of the Harbour forwards who had won four lineouts against the throw.
There was an unacceptably long delay when Harbour were denied a try by the television match official James Slater early in the second spell but justice was done straight after when prop Greg Pleasants-Tate crashed over from a forward drive.
And the deficit was reduced to three points after nine minutes when Parsons crashed over after clever lineout interplay with Minihera and Rei converted from the sideline.
But Northland restored order when flanker Dan Pryor received the ball from a ruck, beat the tackle of Irwin Finau and showed excellent pace to sprint 50m for the bonus point try.
Harbour's plight became worse when openside flanker Zac Judge was red carded - the first ordering off of the competition - by referee Chris Pollock 15 minutes from the end for a tip tackle on Ranger. Ranger himself was binned two minutes later for a professional foul and it became 14-a-side.
Replacement first-five Elrick kicked two penalties in quick succession and Northland were sweating on a four-point nine minutes from the end but Seymour kicked his third penalty to give the Taniwha a seven-point buffer.
But then came Saili's clean break, Elrick's superb conversion and both teams left the ground with three points.
North Harbour 33 (J. Manihera, G. Pleasants-Tate, J. Parsons, N. Tuitavake tries, C. Rei con, pen, J. Elrick con, 2 pens)
Northland 33 (R. Caucaunibuca 2, W. Meltzer, D. Pryor tries, B. Seymour 2 con, 3 pens).
HT: 20-8.