The Vikings, who went into the game needing to win all three of their remaining fixtures to maintain any hope of top flight survival, had former Kiwi test centre Krisnan Inu in hat-trick form as they edged nervously to their first league win since March.
Fax, who were without key loose forward Simon Grix and omitted on loan full back Kieren Moss, worked as hard as ever, but ultimately it was a tale that has been too familiar over the last six weeks as they paid the price for being unable to convert pressure into points.
It was the home side who seized an early lead, with the visitors, who had already had a Shane Grady touchdown chalked off by the video referee, largely the authors of their own misfortune with some crucial unforced errors.
A crazy offload from Dan Fleming 10 metres from his own line paved the way for Weller Hauraki’s opening try, with Inu kicking the conversion.
And when a mix up between Will Sharp and James Woodburn-Hall, both players going for Finn’s kick, saw the ball end up on the floor, Inu trampled a couple of defenders to score in the corner, with the missed conversion leaving Fax trailing 10-0 inside the first quarter.
Slowly, Fax were finding their feet and although their attacking game looked a little blunt, with Widnes easily dealing with their attempts to shift the ball to the edges, they finally cracked their hosts five minutes before the break.
Scott Murrell was the architect, finding Woodburn-Hall with a neat inside ball and the Londoner barrelling over a couple of defenders to score.
Grady converted against his hometown club for 10-6 and the visitors kept the pressure on until the break, the hooter sounding with the Vikings under the cosh.
It was Widnes who opened the second half scoring through Patrick Ah Van, frustratingly from more errors - Saltonstall turning the ball over and Ben Heaton coming in from centre but failing to nail his man - with Inu’s sideline kick putting them 16-6 up.
Fax were still very much in the game, but their lack of edge meant they couldn’t add to their tally and when Inu completed his hat trick from an Ah Van knock down and converted again, the Vikings were home and hosed at 22-6 with 17 minutes remaining.
Fax did get some reward for their undoubted endeavour when Woodburn-Hall’s break created the position for Heaton put Saltonstall over in the corner, Murrell converting to make it 22-12 with five minutes to go.
But it was Widnes who sealed the points with Ah Van’s last minute try, maintaining their tenuous survival hopes.
Widnes: Mellor; Ah Van, Inu, Runciman, Buckley; Lyons, Finn; Gubb, White, Houston, Hauraki, Hansen, Leuluai. Subs: Walker, Chapelhow, Olbison, Wilde
Halifax: Sharp; Saltonstall, Heaton, Butler, Woodburn-Hall; Murrell, Johnston; Fleming, Kaye, Fairbank, Tangata, Grady, Davies. Subs: Jones, Moore, Cooper, Maher
Referee: G. Hewer