AC Not Cooling or Not Blowing Cold Air? 12 Causes Our Techs Find Most Often
• By the First Call Air Conditioning & Heating Repair technical team
When the air conditioner runs but the air at the vents is warm, the cause is almost always in one of four buckets: airflow, refrigerant, electrical, or controls. Here is the order our technicians actually work through.
Five things you can safely check in five minutes
- Thermostat mode and setpoint. COOL, not FAN or HEAT, and at least five degrees below room temperature. A thermostat left on "fan on" blows room-temperature air all day.
- Air filter. A clogged filter starves the coil, freezes it, and kills cooling. If light won't pass through, replace it.
- Breakers. Check the indoor air handler breaker, the outdoor condenser breaker, and the outdoor disconnect box.
- Outdoor unit. Is the fan spinning? Are the fins packed with dust, cottonwood or pet hair? Rinse gently with a hose, power off.
- Vents and returns. Blocked returns behind furniture can cost you a shocking amount of capacity.
Nine causes that need a licensed technician
- Low refrigerant from a leak. Refrigerant is not consumed. If it's low, there is a leak that must be found and repaired, not just topped off.
- Failed run capacitor. The single most common no-cool failure. The compressor hums but won't start.
- Burned contactor. Pitted contacts stop the outdoor unit from energizing at all.
- Frozen evaporator coil. Ice blocks all airflow. Thawing is step one; the airflow or charge problem behind it must be fixed.
- Bad condenser fan motor. No airflow across the coil means the system trips on high pressure.
- Compressor failure. The expensive one. Sometimes repairable, often a replacement decision.
- Blower motor or ECM module failure. Cold coil, no air movement.
- Clogged condensate drain and tripped float switch. A safety device cuts cooling to prevent water damage.
- Leaky or undersized ducts. Cooling made in the attic that never reaches the room.
What a proper diagnosis looks like
Our technicians measure superheat and subcool, static pressure, capacitor microfarads and motor amp draw, then write the numbers down and show you. That's how you avoid paying for parts your system never needed. See our AC repair service or book a seasonal AC tune-up before the next heat spike. Find your city on our locations page.
Need help now? We answer 24/7 for same day AC repair, furnace repair and emergency HVAC service in every California and New York city. Call (209) 309-1834 (CA) or (329) 202-9924 (NY), or find your city.