AC Not Cooling the House
When your AC runs but doesn't cool, the cause is usually something you can check yourself: a dirty filter restricting airflow, a tripped breaker to the outdoor unit, a frozen evaporator coil, or a thermostat issue. Refrigerant problems require a tech.
Step-by-Step Fix
- 1
Check the thermostat
Make sure it's set to COOL (not HEAT or FAN), and the set temperature is below current room temperature. Replace the batteries. If you have a smart thermostat, check that it hasn't lost its schedule or Wi-Fi connection.
- 2
Replace or clean the air filter
A clogged filter is the most common cause of reduced cooling. Find the filter (usually in the return air vent or air handler), pull it out, and hold it to a light. If you can't see through it, replace it. Use a MERV 8–11 filter for best airflow.
- 3
Check the outdoor condenser unit
Go outside and look at the condenser (the large unit with a fan on top). Make sure the fan is spinning. Clear any leaves, grass, or debris from the sides — the unit needs at least 2 feet of clearance all around.
- 4
Check for a frozen evaporator coil
Look at the refrigerant lines going into your house (the larger insulated pipe). If it's covered in ice or frost, you have a frozen coil. Turn the AC off but leave the fan on to thaw it — this takes 1–3 hours. A dirty filter or low refrigerant are the two causes.
- 5
Check the disconnect and breaker
At the outdoor unit, there's usually a disconnect box on the wall nearby. Open it and check that the disconnect is properly seated. Also check your breaker panel for a tripped 'AC' or 'condenser' breaker.
⚠️ Safety Notes
- Don't run the AC with a frozen coil — you can damage the compressor.
- Never use refrigerant cans sold at auto stores — they can damage your system and are illegal to vent.
When to Call a Pro
If the coil freezes again after thawing with a clean filter, you likely have a refrigerant leak — call an HVAC technician. Same if the outdoor fan isn't spinning or you hear grinding/screeching from the condenser.
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