Help? After heating the house for a couple of hrs, I turned the switch to the off position. Usually the fan turns of 20-30 sec later. This time is didn't. Also, at the same time, the unit flashed filter and my husband reset timer to 0. (supposedly the flashing filter doesn't affect the performance of the stat anyway) The fan continued to run and blow cold air and finally we had to turn off the power to the furnace in the garage