Lennox A/C unit: Model HS23-311-2P Everything has power, its just the fan sometimes does not come on, pushed the reset button the fan came on once, and by Tuesday it stopped pushed reset heard condenser but fan didn't come on may have to manually push fan? What makes this stop? Should it be taken off and cleaned seems to be a little tight? Have power in and out changed out thermostat previous Friday. Help Please!