AC Not Working in House: Troubleshooting & Fixes

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Quick answer
Confirm the symptom
Tools and prep
Step-by-step troubleshooting
Common causes table
Parts matching
When to call a pro
FAQ
Related guides

Quick answer

If your AC isn't working, first check the thermostat settings and ensure the power is on. Then inspect the circuit breaker and air filter. If these are fine, the issue may be with the outdoor unit or refrigerant levels.

Confirm the symptom

No cool air coming from vents
AC doesn't turn on at all
Thermostat shows no response
Clicking sound but no compressor startup
Outdoor unit is silent or not running

Tools and prep

Thermostat
Screwdriver
Flashlight
Circuit breaker panel access
New air filter (if needed)
Safety gloves and glasses
Voltage tester (optional)

Step-by-step troubleshooting

Check Thermostat Settings
Do: Verify the thermostat is set to 'Cool' and the temperature is lower than the room temperature.
Observe: Thermostat displays correct settings and responds to changes.
Means: Thermostat is functioning correctly.
Next: Check power supply
Check Power Supply
Do: Ensure the AC is receiving power by checking the circuit breaker and any switches near the outdoor unit.
Observe: Breaker is in the 'on' position and outdoor unit has power.
Means: Power supply is intact.
Next: Inspect Air Filter
Inspect Air Filter
Do: Remove and examine the air filter for dirt or blockage.
Observe: Filter is clean and allows airflow.
Means: Airflow is not restricted by the filter.
Next: Check Outdoor Unit
Check Outdoor Unit
Do: Look at the outdoor unit for obstructions, ice buildup, or tripped switches.
Observe: Unit is clear of debris and switches are in the 'on' position.
Means: Outdoor unit is accessible and ready to operate.
Next: Test Compressor
Test Compressor
Do: Listen for the compressor to start when the thermostat calls for cooling.
Observe: Compressor starts and runs smoothly without unusual noises.
Means: Compressor is functioning properly.
Next: Check Refrigerant Levels
Check Refrigerant Levels
Do: Look for signs of refrigerant leaks, such as hissing sounds or ice on the coils.
Observe: No visible leaks or ice buildup.
Means: Refrigerant levels are likely sufficient.
Next: Contact a Professional
Contact a Professional
Do: If previous steps don't resolve the issue, call a licensed HVAC technician.
Observe: Professional diagnosis and repair are needed.
Means: The problem is beyond basic troubleshooting.
Next: None

Common causes

Cause	Likelihood	Difficulty	Part often needed
Thermostat Issues Incorrect settings or a faulty thermostat can prevent the AC from activating.	Common	Easy	Thermostat replacement or calibration
Tripped Circuit Breaker A tripped breaker cuts power to the AC system.	Common	Easy	Reset circuit breaker
Dirty Air Filter A clogged filter restricts airflow and reduces cooling efficiency.	Common	Easy	New air filter
Outdoor Unit Problems Obstructions, ice, or a tripped switch can prevent the outdoor unit from operating.	Sometimes	Easy–Medium	Outdoor unit cleaning or switch reset
Compressor Failure A faulty compressor can't circulate refrigerant, preventing cooling.	Sometimes	Hard	Compressor repair or replacement
Low Refrigerant Levels Low refrigerant reduces cooling capacity and can indicate a leak.	Sometimes	Hard	Refrigerant recharge and leak repair
Wiring or Electrical Issues Loose or damaged wiring can disrupt the AC's operation.	Rare	Hard	Electrical repair or replacement
Faulty Capacitor A failed capacitor prevents the compressor and fan from starting.	Rare	Medium	Capacitor replacement
Blocked Condensate Drain A clogged drain can cause water buildup and system shutdown.	Rare	Easy–Medium	Drain cleaning kit
Old or Worn-Out System An aging AC system may fail due to wear and tear.	Rare	Hard	AC system replacement

Parts matching

Common parts needed for AC not working in house issues:

Thermostat
Air filter
Circuit breaker
Outdoor unit cleaning kit
Capacitor
Refrigerant recharge kit
Drain cleaning kit

Always match parts to your specific AC model and consult a professional for refrigerant or electrical repairs.

When to call a professional

AC doesn't turn on after checking power and thermostat
Compressor doesn't start or makes loud noises
Refrigerant leaks or ice buildup persists
System is over 10 years old and frequently breaks down
You suspect electrical or wiring issues
You're unsure about handling refrigerant or high-voltage components

FAQ

How often should I replace my air filter?

Replace your air filter every 1–3 months, depending on usage and filter type.

Can a tripped circuit breaker cause my AC to stop working?

Yes, a tripped breaker cuts power to the AC. Reset it if it's in the 'off' position.

Why is my AC making noise but not cooling?

Noise without cooling could indicate a faulty compressor, low refrigerant, or electrical issues.

How do I know if my thermostat is faulty?

If the thermostat doesn't respond to changes or shows incorrect temperatures, it may be faulty.

Is it normal for the outdoor unit to get hot?

Yes, the outdoor unit gets hot during normal operation, but excessive heat or noise may indicate a problem.

Can I recharge refrigerant myself?

Refrigerant recharge requires specialized tools and licensing. Always hire a professional for this task.