Why Is My AC Not Cooling?
Change the filter, clear debris from the outdoor unit, and confirm the thermostat is set to COOL with the setpoint below room temperature. If none of those restore cooling within an hour, the system has a real problem (most often a run capacitor, dirty condenser coils, or a refrigerant leak) and you should call us at 602-560-8989. In a Phoenix summer, indoor temperature climbing past 85°F is a heat-safety issue.
Common Causes
Dirty Air Filter
A clogged filter restricts airflow, forcing the system to work harder while delivering less cooling. In Phoenix's haboob and construction-dust loads, a filter that lasts three months in mild climates may need replacing every 4 to 6 weeks once the system is running daily. The first thing to rule out on a no-cool call.
Failed Run Capacitor or Contactor
When the run capacitor weakens below its rated microfarad value, the compressor struggles to start, may trip on thermal overload, or fails to start at all. The indoor blower keeps running while the outdoor unit sits quiet or hums. When the contactor's contacts pit or stick, the compressor engages intermittently or not at all. Monsoon-season ant intrusion is a recurring cause in Phoenix.
Dirty Condenser Coils
The outdoor coil releases heat from the refrigerant. When monsoon dust and debris coat the fins, the system can't shed heat and indoor cooling drops. Rinsing fins with a garden hose (top down, never a pressure washer) helps. A full coil service includes foaming cleaner, fin straightening, and a pressure check, which is what restores rated capacity.
Low Refrigerant from a Leak
Refrigerant circulates in a sealed loop and is never consumed. If the system is low, there is a leak somewhere (Schrader valve, flare fitting, coil joint, or line set). Symptoms include ice on the refrigerant lines, cooling that drops off as the day heats up, or longer run times for the same setpoint.
Frozen Evaporator Coils
Ice on the indoor coil blocks airflow. The two common causes: a restricted filter (back to #1) and a refrigerant charge problem. If you see ice, turn the system off at the thermostat. Don't chip at the ice. The aluminum fins bend easily and a damaged evaporator usually means coil replacement.
Thermostat Misconfiguration
Dead batteries, set to HEAT or FAN instead of COOL, or a setpoint above the current room temperature are all surprisingly common. Verify the basics before assuming the AC has failed.
What Should You Do?
Try This First
- Change the air filter (the most common fix; do this first)
- Verify the thermostat is set to COOL and the setpoint is below current room temperature
- Look at the outdoor unit. Clear leaves, cottonwood fluff, or anything covering the top or pressed against the sides
- Hold your hand to a supply vent. You should feel air moving, even if it isn't cold
- If you see ice on the refrigerant lines or the indoor coil, turn the system off at the thermostat and call us before the ice damages the coil
Call a Pro If...
- AC runs constantly but never reaches the thermostat setpoint
- Indoor temperature is climbing above 85°F (heat-safety issue in summer)
- You see ice on the refrigerant lines or outdoor unit
- The outdoor unit is silent but the indoor blower runs
- A fresh filter and clear outdoor unit did not restore cooling within an hour
- Warm air from the supply vents with the system running
- System short-cycles (turns on and off every few minutes)