What's wrong with my central air unit when the fan on the outside unit does not operate?

Answer 1

It can be a variety of things. First, is the compressor running? That's in the condenser(outside unit) an if it's running you'll hear it, it'll make a fairly loud humming noise. If it's just the fan not running it could be a bad motor, capacitor, wiring connection or control. If nothings running it could be as simple as a bad thermostat, or it's not set properly, or breaker is off or faulty. Depending on what skills you have, and if you own a GOOD multimeter or not it's beat to call a pro after you check the simple things. I can't tell you how many people end up spending twice what it would have been by trying to fix it themselves.