Service AC Not Blowing Cold Air

Quick answer

Check the thermostat setting, air filter, and ensure the AC is receiving power. If the outdoor unit is running but no cold air comes out, the refrigerant might be low or the compressor could be faulty.

Confirm the symptom

• AC is running but not blowing cold air
• Outdoor unit is running but no cold air from vents
• Thermostat is set to cool but no cold air
• Air is blowing but feels warm or room temperature

Tools and prep

• Infrared thermometer — Check air temperature at vents
• Screwdriver set — Access internal components
• Shop vacuum or soft brush — Clean air filter and coils
• Thermal imaging camera — Detect airflow and temperature issues
• Refrigerant leak detector — Identify refrigerant leaks

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Prep & safety

• Turn off the AC power at the circuit breaker to avoid electrical hazards.
• Ensure the area around the outdoor unit is clear for access.
• Wear gloves and safety glasses to protect against sharp parts and debris.

Step-by-step troubleshooting

1. Check Thermostat Settings
   Do: Verify the thermostat is set to 'Cool' and the temperature is lower than the room temperature.
   Observe: Thermostat is set correctly.
   Means: Thermostat is not the issue.
   Next: Check air filter
2. Check Air Filter
   Do: Inspect and clean or replace the air filter if it's dirty or clogged.
   Observe: Air filter is clean and unobstructed.
   Means: Improved airflow may resolve the issue.
   Next: Check outdoor unit
3. Check Outdoor Unit
   Do: Ensure the outdoor unit is running and not overheated or blocked.
   Observe: Outdoor unit is running and free of debris.
   Means: Outdoor unit is functioning properly.
   Next: Check refrigerant level
4. Check Refrigerant Level
   Do: Use an infrared thermometer to check the temperature difference between the inlet and outlet of the evaporator coil.
   Observe: Temperature difference is less than 15°F (8°C).
   Means: Refrigerant may be low.
   Next: Check for refrigerant leaks
5. Check for Refrigerant Leaks
   Do: Use a refrigerant leak detector to scan for leaks in the refrigerant lines.
   Observe: No visible leaks or hissing sounds.
   Means: No refrigerant leaks detected.
   Next: Check compressor
6. Check Compressor
   Do: Listen for the compressor starting up in the outdoor unit.
   Observe: Compressor is not running or making unusual noises.
   Means: Compressor may be faulty.
   Next: Call a professional
7. Check Blower Fan
   Do: Inspect the blower fan for obstructions or damage.
   Observe: Blower fan is clean and spinning freely.
   Means: Blower fan is functioning properly.
   Next: Check electrical connections
8. Check Electrical Connections
   Do: Inspect electrical connections for loose or damaged wires.
   Observe: All connections are secure and undamaged.
   Means: Electrical connections are not the issue.
   Next: Call a professional

Common causes

Parts you might need

When replacing parts, ensure compatibility with your AC model and specifications.

• Air filter: match size (e.g., 16x25x1) and type (e.g., pleated, HEPA).
• Refrigerant: match type (e.g., R-410A, R-22) and system requirements.
• Thermostat: match compatibility with your AC system and features (e.g., programmable, smart).
• Blower fan motor: match voltage, RPM, and mounting dimensions.
• Evaporator coil cleaning kit: match coil size and cleaning solution compatibility.
• Compressor: match model number, voltage, and system compatibility.
• Electrical wiring: match gauge, voltage rating, and connection type.

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Consult your AC's user manual for specific part numbers and specifications.

When to call a professional

• If refrigerant is low and you can't find the leak.
• If the compressor is not running and you hear unusual noises.
• If the evaporator coil is frozen and defrosting doesn't help.
• If electrical issues are suspected beyond basic checks.
• If the problem persists after checking all DIY steps.

FAQ

Related guides

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• AC not cooling house
• AC not blowing air