Please help. During the last few days we've had 100+degree days. Our cent air unit shut off n on due to lack of power I assume, now it wont even turn on. since everyone had their ACs on. I flipped the switch and all I hear is this buzzing. Installed fresh batteries in the thermostat. Didnt help.Now I have read similar problems and their solution was changing out the capacitors. I did see that the one person tried to nudge the fan. I also tried but without success.But the contactor relay is whats doing the buzzing. My question is: what do I change to fix the unit ?