If your outside AC unit isn’t turning on, common causes include a tripped circuit breaker, blown fuse, or thermostat issues. A faulty contactor or capacitor can also prevent the unit from starting. Additionally, the unit may be receiving no power due to a disconnected or damaged power line. Dirty coils, clogged filters, or refrigerant leaks can trigger safety shut-offs. Sometimes, a simple issue like a switched-off disconnect box or an incorrectly set thermostat is to blame. Regular maintenance and timely inspections help prevent such problems and ensure your AC runs efficiently. If unsure, consult a licensed HVAC technician for diagnosis.