10 Common Air Conditioner Problems (And How to Fix Them Yourself!)

Air conditioners can develop issues over time, but many problems have simple DIY fixes before calling a professional. Here are 10 common AC problems and how you can troubleshoot them yourself.

1. AC Not Turning On

Possible Causes:

Tripped circuit breaker

Blown fuse

Faulty thermostat

Power switch turned off

How to Fix:

✔ Check the circuit breaker and reset if tripped.

✔ Replace a blown fuse.

✔ Ensure the thermostat is set to “Cool” and has fresh batteries.

✔ Verify the outdoor unit’s power switch is on.

2. Weak Airflow

Possible Causes:

Clogged air filter

Blocked vents or ducts

Faulty blower fan

How to Fix:

✔ Replace or clean the air filter (every 1-3 months).

✔ Ensure vents are open and unobstructed.

✔ Check the blower fan for debris or damage.

3. AC Blowing Warm Air

Possible Causes:

Dirty air filter

Low refrigerant levels

Frozen evaporator coil

Outdoor unit issues

How to Fix:

✔ Replace the air filter.

✔ Check if the outdoor unit is running (if not, reset the breaker).

✔ If the evaporator coil is frozen, turn off the AC and let it thaw.

✔ If refrigerant is low, call a professional (handling refrigerant requires certification).

4. AC Leaking Water

Possible Causes:

Clogged condensate drain line

Frozen evaporator coil

Broken condensate pump

How to Fix:

✔ Unclog the drain line with a wet/dry vacuum or bleach solution.

✔ If the coil is frozen, turn off the AC and let it thaw.

✔ Check the condensate pump (if installed) for proper operation.

5. AC Making Strange Noises

Possible Causes:

Banging: Loose or broken parts

Squealing: Worn-out belt or motor bearings

Clicking: Faulty relay or electrical issue

Hissing: Refrigerant leak

How to Fix:

✔ Tighten loose screws or bolts.

✔ Replace a worn-out belt (older units).

✔ If refrigerant is leaking, call a professional.

6. AC Short Cycling (Turning On/Off Frequently)

Possible Causes:

Dirty air filter

Low refrigerant

Oversized AC unit

Faulty thermostat

How to Fix:

✔ Clean or replace the air filter.

✔ Check thermostat placement (avoid heat sources).

✔ If the unit is too large, consult an HVAC technician.

7. Frozen Evaporator Coil

Possible Causes:

Low refrigerant

Poor airflow (dirty filter or blocked vents)

Faulty blower motor

How to Fix:

✔ Turn off the AC and let the ice melt.

✔ Replace the air filter.

✔ Check refrigerant levels (call a pro if low).

8. AC Smells Bad

Possible Causes:

Musty smell: Mold in the ducts or drain pan

Burning smell: Electrical issue

Rotten egg smell: Dead animal in the ductwork

How to Fix:

✔ Clean the drain line with bleach.

✔ Replace the air filter.

✔ If electrical, turn off the AC and call a technician.

9. Thermostat Not Working

Possible Causes:

Dead batteries

Incorrect settings

Loose wiring

How to Fix:

✔ Replace thermostat batteries.

✔ Ensure it’s set to “Cool” and the right temperature.

✔ Check wiring connections.

10. High Energy Bills

Possible Causes:

Dirty air filter

Leaky ducts

Old, inefficient AC unit

How to Fix:

✔ Replace the air filter regularly.

✔ Seal duct leaks with foil tape or mastic.

✔ Consider upgrading to an energy-efficient model.