The Rebels were on course their third win in a week when Ashton allowed an overhit pass to zip past him off the greasy surface, leaving Dave Foster to fire home from a narrow angle.
FC had earlier come from behind to lead 2-1 through Adam Carden and Jamie Baguley, but Foster's late leveller forced them to settle for a point.
The 2-2 draw was a major missed opportunity for Karl Marginson's men as UniBond division one north leaders Skelmersdale, who they visit tomorrow, were also held, at Ossett.
It also enabled third-placed Curzon Ashton to stretch their lead over FC to six points with a 4-2 win at Harrogate Railway.
Meanwhile, Blue Square North-bound Witton Albion regained their stranglehold on the UniBond premier title with Adam Warlow's hat-trick helping them thrash Lincoln 6-0, while relegation-threatened Ashton United came from two-down to draw 2-2 with visiting Kendal.
Vodkat League champions-elect Trafford seized on Salford's 2-2 draw at Newcastle to march 12 points clear of them at the summit by winning 2-1 at Winsford.
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