Air Conditioner Not Cooling — compressor, evaporator coil

Use only checks that match the exact appliance or system and its official guide.

1. Check 1

   With cooling selected and no immediate hazard, observe one or more supply registers and the return. Note whether the indoor blower is silent, airflow is weak, or airflow is normal but the air remains warm; do not remove covers or reach into a grille.

   Expected result: Airflow is absent, weak, or normal while the room remains warm.

   Next step: Follow the matching branch and keep the system off if ice, water, odor, noise, or electrical symptoms are present.

   Why this matters

   Why: Absent or weak airflow shifts attention toward the filter, blower, duct path, drain safety, or frozen evaporator coil. Normal airflow with warm air shifts attention toward the outdoor unit, compressor, condenser, refrigerant circuit, or controls.

2. Check 2

   Check that the thermostat is in cooling mode with a setpoint below the indoor temperature and that the fan setting is understood. From a safe, dry location, inspect the accessible filter and visible return or supply openings; replace the filter only if the exact equipment instructions allow it and the replacement has the correct size and airflow direction.

   Expected result: The thermostat is not calling for cooling, the filter is dirty or blocked, or these visible items look normal.

   Next step: Correct only a clear setting or accessible filter issue, then allow one normal cooling call. If cooling remains poor, stop repeating the check and arrange HVAC service.

   Why this matters

   Why: A setting or restricted filter can explain poor cooling and airflow. If the settings and filter are normal but the symptom continues, the cause is not confirmed by this check and may involve the coil, compressor, refrigerant, or controls.

3. Check 3

   From outside the indoor cabinet, look for frost or ice on accessible refrigerant tubing, the cabinet exterior, or nearby surfaces, and look for unusual condensate or meltwater. Do not open the coil cabinet, chip ice, apply heat, or touch tubing.

   Expected result: Ice or frost is visible, airflow is very low, condensate is excessive, or there is no ice or unusual water.

   Next step: If ice or water is present, turn cooling off from the thermostat, protect the area from meltwater, and arrange HVAC service before restarting. If no ice is visible, continue with the safe outdoor observation.

   Why this matters

   Why: Ice can accompany restricted airflow, a dirty coil, low refrigerant, or another fault; water may appear as ice thaws. The absence of visible ice does not rule out a coil, compressor, or refrigerant issue.

4. Check 4

   From a safe distance, observe whether the outdoor unit starts during a valid cooling call, whether its fan runs normally, and whether there is unusual noise, smoke, ice, or a short-cycle pattern. Do not touch the fan, grille, disconnect, wiring, capacitor, contactor, compressor, or refrigerant lines.

   Expected result: The outdoor unit is silent, starts and stops quickly, runs continuously without cooling, makes abnormal noise, or appears to run normally while indoor air remains warm.

   Next step: Keep the system off for abnormal noise, ice, smoke, odor, or repeated cycling and arrange qualified HVAC service. Do not reset or open the outdoor unit to compare behavior.

   Why this matters

   Why: A no-start or short-cycle pattern can involve power, controls, capacitor, contactor, fan, compressor, or refrigerant. Continuous operation with warm air can fit low refrigerant, coil, condenser, airflow, or compressor trouble; visual observation alone cannot identify the failed part.

5. Check 5

   Record the equipment nameplate information, thermostat mode and setpoint, filter condition, indoor airflow, outdoor-unit behavior, runtime pattern, ice or water location, and any breaker or disconnect event. Note whether the problem is constant, intermittent, or tied to a hot period.

   Expected result: The record points to weak airflow, ice or water, a normal-airflow warm-air pattern, outdoor no-start, short cycling, or an electrical symptom.

   Next step: Provide the record to qualified HVAC service. Include refrigerant information only as shown on the nameplate or manual; do not open the circuit or add refrigerant.

   Why this matters

   Why: A clear symptom pattern helps a technician separate airflow and evaporator-coil concerns from compressor, condenser, refrigerant, control, or supply concerns without the user entering a hazardous area.

6. Check 6

   After the safe external checks, decide whether the issue requires a sealed-system or electrical diagnosis: compressor, evaporator coil, refrigerant, contactor, capacitor, wiring, or control work. Do not remove the cabinet, attach gauges, or work on the sealed refrigeration circuit or electrical system.

   Expected result: A professional component or sealed-system fault is suspected, or the thermostat, filter, and visible air path were normal but cooling did not recover.

   Next step: Keep cooling off when the fault is persistent or unsafe and arrange qualified HVAC service; use certified refrigerant service for refrigerant work.

   Why this matters

   Why: These observations are a service trigger, not proof that a particular part has failed. A qualified technician must test the system and determine whether repair, leak correction, or another remedy is appropriate.