Most no-cool calls have one of these seven causes. Some you can fix yourself in 5 minutes.
1. Tripped Breaker
Outdoor condensers have their own breaker. If it's tripped, reset it once — if it trips again, stop and call a pro. Repeated tripping usually means a failing compressor or shorted wire.
2. Clogged Filter
A filter that's been in for 6 months can freeze the evaporator coil and cause the system to blow warm. Replace and let the system thaw 1-2 hours.
3. Thermostat Settings
Confirm the system is on COOL (not FAN or HEAT) and the setpoint is below room temperature. A surprising number of calls are this simple.
4. Frozen Indoor Coil
Look at the copper line outside — if it's iced, turn the system OFF and the fan ON for 2 hours. Common causes: dirty filter, low refrigerant, dirty coil.
5. Dirty Condenser
If the outdoor unit's fins are caked with pollen, leaves, or dryer lint, the system can't dump heat. Rinse gently with a garden hose from the inside out.
6. Low Refrigerant
If the system is more than 5 years old and cooling has slowly degraded, you may have a slow refrigerant leak. This needs a pro — refrigerant is not a DIY repair.
7. Failed Capacitor
If the outdoor fan isn't spinning but the system is humming, the run capacitor is the #1 culprit. Inexpensive part, easy fix for a tech.
