Easy Troubleshooting for Common AC Problems

Key Takeaways

• A dirty filter is the cause of 50% of AC service calls — check yours first
• Thermostat set wrong, tripped breaker, and dirty condenser solve most "AC not cooling" complaints
• Ice on the lines usually means low airflow or low refrigerant — turn the system off immediately
• Know which fixes are safe DIY and which require a licensed technician

Your AC stopped working on the hottest day of the year. Before you panic and call for emergency service, run through these troubleshooting steps. Half of all AC service calls are caused by issues homeowners can fix themselves in minutes.

AC Not Turning On

Check the thermostat. Is it set to "cool"? Is the set temperature below the current room temperature? Is the fan set to "auto"? These sound obvious, but they account for a surprising number of service calls.

Check the breaker. Your AC runs on a dedicated 240V breaker. A tripped breaker is common after power surges. Find your electrical panel and look for a breaker that's in the middle position (tripped). Flip it fully off, then back on. If it trips again immediately, stop — you have an electrical issue that needs a technician.

Check the disconnect switch. There's an outdoor disconnect box near the condenser unit. Make sure it hasn't been switched off by a previous contractor or homeowner.

AC Running but Not Cooling

Replace the filter. A severely clogged filter restricts airflow so badly that the evaporator coil can't absorb heat. Replace the filter and give the system 30 minutes to recover.

Clean the outdoor condenser. If the condenser coils are coated in cottonwood fluff, grass clippings, or dirt, the system can't reject heat. Gently hose down the condenser fins from inside out with a garden hose. Don't use a pressure washer — it bends the fins.

Check the vents. Are supply vents open in all rooms? Closed or blocked vents increase system pressure and reduce cooling capacity. Furniture over vents is a common culprit.

Ice on the Refrigerant Lines

If you see ice forming on the copper lines between the indoor and outdoor units, or on the indoor coil, turn the system off immediately. Running with ice damages the compressor. Two common causes:

• Restricted airflow: Dirty filter, closed vents, or a failing blower motor. Replace the filter, open all vents, and let the ice melt completely (this can take 2–4 hours) before restarting
• Low refrigerant: A refrigerant leak requires a licensed technician. If replacing the filter doesn't fix the icing, call for AC repair service

Strange Noises

• Buzzing from outdoor unit: Often a contactor relay vibrating — needs replacement ($100–$200)
• Squealing or screeching: Belt or bearing issue in the blower motor. Turn off the system to prevent further damage
• Clicking at startup: Normal. Persistent clicking without startup suggests a relay or control board failure
• Banging or clanking: A loose or broken component inside the compressor or blower. Turn off and call a technician
• Hissing: Refrigerant leak. Turn off and call immediately

Water Leaking from Indoor Unit

Your AC produces condensation — that's normal. The water should drain through a condensate line to a floor drain or pump. If water is pooling around the indoor unit, the condensate drain is likely clogged. You can clear it by pouring a cup of white vinegar through the drain line access point. If the drain pan is rusted through or cracked, it needs replacement.

When to Call a Professional

Call for professional AC repair when: the breaker keeps tripping, you smell burning, ice persists after a filter change, refrigerant is leaking, or any component inside the unit needs replacement. Refrigerant handling, electrical work, and compressor issues all require licensed technicians.

Frequently Asked Questions

Still Not Working?

If these steps didn't solve it, request a service call or call 1-855-539-4328. We offer same-day emergency AC repair across the GTA.

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