Hi there. I have a condo-sized central A/C situated in the hallway ceiling. It's about 10yrs old. My thermostat is there also. After being out of town for a few weeks, I returned to see that batteries in the thermostat had run down and were flashing. No problem I thought. I inserted fresh batteries, made sure that the cool and fan settings were set and all I heard was a click from the ceiling unit overhead - as if it was trying to engage. Nothing else. Does this sound like an obvious fix? Did the fact that the batteries in thermostat which I kept at 78 powered-out for an unspecified period affect the unit? Does this sound like a complicated repair? Thanks again, any help is greatly appreciated.

A click from the T'stat indicates power to the contactor. A click from the condenser means it has closed or at least tried. Where is your condenser, surely not in the attic?

Thanks for replying.. I'm not technical.. It's a condo - the condenser I believe is right overhead and easily accessible and within reach when I change the filter. It's the equivalent of about 2 feet above my head.. and that's why I can hear it "clicking" on so easily... but no fan action at all.

I think you are confusing the condenser with the evaporator/air handler. Because of the heat generated in the condensing stage, they are typically located outside. In an attic, it would be hard to condense the hot gas back to a liquid.
You may have something special but the condo's I have been in had the Condensers outside. It could be a capacitor or you are hearing the motor try to start but the thermal overload, which could be the click, turns off the power. Who owns the AC, you or the Condo Assoc.