So yesterday my wife turned on the central air. It started up fine, then a minute or so later, it shutdown suddenly. I took a look at the thermostat, and it looked like it should be cooling.

I then switched it from "Auto" to "On", figuring the fan would start blowing, but it didn't, it did absolutely nothing. The compressor doesn't come on, and the fan doesn't come on.

I reset the thermostat (it's digital. The whole system is about 5 years old). When it's on Auto and I turn the temperature setting down low, I can hear the thermostat click like it's trying to turn on the air, but the compressor and the blower do not start.

I checked the electrical panel, everthing was fine. Any ideas on where to start troubleshooting? This is an attic-installed blower with an integrated heater. I'm thinking I'll try to turn on the heat when I get home and see if that gets the blower going, but I have a feeling it won't help...

No compressor and no fan sound like a fuse on the unit itself. You may also have a localized breaker near the AC, so check for that also. If the fan doesn't come on for the heat either, then I'd really expect it to be local to the equipment. Make sure you have power to the unit and you know it is an HVAC problem.

The only thing that both the inside fan and outside unit have in common electrically is the thermostat and the 24 volt transformer. With a volt meter, check between the red wire and yellow wire of the thermostat. If you have 24 volts
between them check between the red and green wire if 24 volts present you have a bad thermostat if no voltage at either you have a bad transformer or bad circuit wiring to the thermostat . The air handlers do vibrate some so it could be just a wire come loose. Thats my guess
Good luck

Larry

Thanks for the advice...as it turns out, it was a fuse local to the unit. I did try turning on the heat, and that didn't work either, but the fuse did the trick. It just seems bizarre that the compressor wouldn't come on either. Is the thermostat smart enough to not turn on the A/C compressor if the blower isn't working?

Thanks again!