Ed Joyce and Chris Nash both hit half-centuries between interruptions in play, before Nash was bowled by Rob Keogh for 53 before lunch.
Joyce was trapped lbw by Ben Sanderson after the break to give the visitors a slight hope of grasping a win.
Bad light stopped play with the hosts 145-2 as they held on to share the points with no further play possible.
Northants' seventh draw from their eight Division Two matches leaves them seventh and leave them trailing leaders Essex by 34 points.
With only one side promoted from the second tier this season, both sides are struggling, with Sussex lying in sixth position and only three points better off - albeit with a game in hand.
Heavy rain denied Northants the opportunity to push for victory as they drew against Sussex at Arundel.