Most AC failures don't happen without warning — the root cause builds for weeks.
Low refrigerant: The #1 cause of warm air output. Requires EPA 608 certified technician. Expect $150-$400 for recharge plus leak repair.
Dirty condenser coils make your system work 30% harder. Annual cleaning ($150-$300) extends unit life by 5+ years.
Failed capacitor is a $150-$300 same-day fix. Symptoms: AC hums but won't start, trips breaker repeatedly.
Frozen evaporator coil is usually a clogged filter. Change the filter, wait 24 hours, call a tech if the problem persists.
The average AC repair: $300-$500. Full replacement: $3,500-$7,500. Units over 12 years old needing major repairs should be evaluated for replacement.