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Cooling Troubleshooting

AC Running But Not Cooling

Your air conditioner is running, but the home is not cooling properly. Learn the common airflow, refrigerant, outdoor-unit and system-capacity conditions that can cause this symptom.

What It Can Mean

Start with the symptom, then narrow the cause

The fact that the blower or outdoor unit is running does not prove the system is producing full cooling capacity. Cooling depends on both the refrigeration circuit and proper indoor and outdoor airflow.

A thermostat reading that continues to rise or a home that never reaches setpoint can result from a simple restriction or a more significant equipment problem.

Start with safe checks, then avoid guessing at refrigerant or electrical faults without proper measurements.

Possible Causes

Common conditions associated with this symptom

Dirty or restrictive filter

Low return airflow can reduce cooling performance and may contribute to evaporator-coil temperature problems.

Frozen indoor coil

Ice blocks airflow and prevents normal heat transfer. A frozen coil is a symptom that must be corrected, not simply thawed repeatedly.

Outdoor condenser problem

A failed fan, dirty coil, electrical fault or compressor issue can prevent heat from being rejected outdoors.

Refrigerant-related problem

Incorrect refrigerant charge or a leak can reduce system capacity and alter evaporator conditions.

Duct or airflow problem

Restricted returns, damaged flex duct, closed dampers or blower issues can reduce delivered cooling.

System load or sizing

Extreme outdoor conditions, building changes or an improperly sized system can affect the ability to maintain setpoint.

Important

Do not diagnose by symptom alone

Several different HVAC faults can produce the same homeowner symptom. Proper diagnosis may require electrical readings, refrigerant measurements, airflow testing, static-pressure measurements, combustion testing or control-sequence checks.

Do not bypass safeties, open sealed refrigerant circuits, work on gas piping or perform live electrical troubleshooting unless you are qualified to do so.

Call for Service

Professional evaluation is appropriate when

  • The indoor coil or refrigerant line is frozen.
  • The outdoor unit is not running or makes abnormal electrical/mechanical noise.
  • The system runs continuously but cannot maintain temperature.
  • You suspect refrigerant loss, electrical problems or compressor failure.
  • The symptom returns after basic filter and airflow checks.
Need More Help Narrowing It Down?

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Answer a few questions about what your system is doing and get a more targeted list of likely causes, safe checks and related Central HVAC guides.

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Related Troubleshooting

Similar symptoms and system topics

Need Help?

Describe what the system is doing

When requesting service, include the equipment type, approximate age, when the problem started, whether the system still operates and any unusual noise, water, odor or thermostat behavior you have noticed.

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