The full-back's volley snatched a point for the visitors after James Hayter had thought he had given his side the win when he continued his fine goalscoring form with a first-half header.
In a game where chances were few and far between, Hayter needed just one chance to score his fifth goal in as many games.
The striker headed past Swans keeper Dorus De Vries to give the hosts a deserved lead after David Healy had a goal ruled out for being offside.
Healy had several opportunities to put the result beyond doubt for Sean O`Driscoll`s men, but he was foiled by a mixture of poor finishing and fine goalkeeping from De Vries.
He was made to regret those misses when Rangel rifled his volley past Neil Sullivan.
Source: PA
Source: PA