Charmglow Cgn300tq Fan On 'auto' Comes On Automatically But Will Not Turn Off.

The fan on my Charmglow ventless gas fireplace, on auto, will turn on after the fireplace heats up. Good deal. The problem is, when the fire shuts off, the fan keeps running and running, long after it probably should have stopped due to a lower ambient temperature. I cleaned and vacuumed it all up, then used 400 grit sandpaper on the metal piece I've heard referred to as the unit's thermocouple, and got the pilot to stay lit after the gas shuts off, but with the fan continuously running it blows the pilot out. Ideas? Thanks in advance.