In what proved to be a tight and competitive first half, Ashley Elphick had a good chance early on as the ball came through to him in the penalty area but his low shot went wide of the far post.
Chances proved to be limited but Sidley shaded the half with more half chances for Scrace and Funnell cleared away by the Rangers defence and Sanderson striking an effort from distance over the bar.
Rangers failed to really test Sidley goalkeeper Joe Rogers but there was always a sense that they posed danger. Their best move of the half came right before the whistle as a swift break saw an effort from goal looped just wide from around the penalty spot by Dylan Nanuck.
Early in the second period Sidley got away with a rare moment of miscommunication which allowed a cross from the left to find Dan Wilkes but he could only steer his effort wide of Rogers' near post.
Gary Hempe had a piledriving effort from 30 yards tipped over the bar by the goalkeeper as Sidley pressed. With Simon Corke winning headers and Sidley driving on, the asecendancy was with the home side.
And on 78 minutes they got their goal. A cross from the right from George Aston found Funnell who glanced his header past the Rangers goalkeeper to give the Blues the lead.
The game opened up somewhat after that and Sidley had a chance on the break to seal the win from Elphick but his shot was just too high.
Numerous times the offside flag denied both sides getting into dangerous positions as both defences kept high lines and were generally compact.
And that was especially true for Sidley as Rangers couldn't put Rogers under sustained pressure and the Sidley defence, who were resolute throughout, were able to cut out any dangerous balls forward.
Sidley nerves weren't helped by almost 7 minutes of added time but they held out and were good value for the win.
The result means the Blues move level on points with Rangers, who lead the table due to their superior goal difference and who have 1 match remaining. The Blues though have 2 games in hand meaning they require 4 points from their final 3 league matches to be crowned champions.
Sidley Team: Rogers, May, Hempe, Aston, Eldridge, Carey, Sanderson, Elphick, Scrace (Bailey), Corke, Funnell (Day).