I have central ac and I ran the unit yesterday which cooled the house and was working fine... I left the ac unit on and went out for the night returning home the unit was not working and house was very hot. I check the thermostat and fuses on the breaker panel. Everything seems fine.. I went out and check the unit on the side of the house. Unit appeared to be getting power (making a faint buzzing noise at unit) but fan was not turning on. Turned off thermostat and open the windows for the night. What should I check next? Today's going to be HOT!!

Check to see if 24 volts is being applied to the contactor in the outside unit with the power turned on for the inside unit. Also while you are in there look for any burnt wiring or a bad capacitor.