With overnight co-leaders Bernhard Langer and Jay Don Blake among the later starters, and Carl Mason three over for the day with three to play, Pavin took the lead with consecutive birdies from the tenth.
That put the American three under for the day with seven holes remaining and five under over all as Carnoustie continued to provide a tough challenge.
Langer and Blake were alone in second, but Wales' former Masters Tournament champion Ian Woosnam had moved into a share of fourth.
Europe's former Ryder Cup Captain birdied the second, fourth and fifth in a faultless three under 33 on the front nine, and another gain at the 383 yard 11th put Woosnam four under for the day and three under for the tournament.
Also in a share of fourth were the American trio of Mark Wiebe, Larry Mize and Dan Forsman.