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Quick Answer:
What can you fix yourself? Homeowners can safely troubleshoot and address a few basic AC issues without professional help, such as replacing a clogged filter, changing thermostat batteries, or resetting a tripped breaker.
These basic AC troubleshooting and maintenance steps do not require handling refrigerant or servicing high-voltage components. Homeowners can safely perform some simple checks, but electrical work, refrigerant work and repairs involving internal components should be left to a qualified HVAC professional.
Before calling a technician, there are several basic things you can check if your air conditioner is not cooling properly. If the problem persists, returns after a temporary fix, or involves refrigerant, electrical components or internal system parts, stop troubleshooting and contact a qualified HVAC professional.
This guide from LG Home Comfort covers common AC checks and maintenance tasks you can safely perform yourself. You will learn what to check first, how to approach each task and when a problem has reached the point where professional diagnosis or repair is needed.
| DIY check or maintenance task | Estimated time |
|---|---|
| Replace a dirty or clogged air filter | About 5 minutes |
| Reset a tripped circuit breaker | 2 to 5 minutes; reset once only. If it trips again, turn the system off and call a qualified HVAC professional. |
| Allow a frozen evaporator coil to thaw completely | Time varies |
| Check or clear an accessible condensate drain blockage | Time varies |
| Clean around the outdoor condenser unit | 15 to 20 minutes |
| Replace thermostat batteries on compatible battery-powered models | About 5 minutes |
| Straighten minor, accessible condenser-fin bends with the system powered off | Time varies |
Fix 1: Replace the Air Filter
A clogged air filter is a common cause of restricted airflow and reduced air conditioner performance. Replacing a dirty filter usually takes about five minutes and can help restore proper airflow. If a filter becomes heavily restricted, reduced airflow can contribute to poor cooling, coil freezing, or other operating problems. It is one of the simplest checks to make when your air conditioner is not cooling properly.
To learn more about choosing and replacing filters, see our guide on furnace filters and when to replace them.
How to Replace the Air Filter
- Turn the system off at the thermostat.
- Locate the filter at the return-air grille, filter cabinet, or designated filter slot near the furnace or air handler.
- Check the filter size and follow the equipment manufacturer’s recommended filter type and MERV rating.
- Replace disposable fiberglass and pleated filters rather than washing or reusing them, unless the manufacturer specifically states that the filter is reusable.
- Install the new filter with the arrow pointing in the direction of airflow. Follow the airflow marking on the old filter or your equipment manufacturer’s instructions if you are unsure.
- Restart the system and check that airflow is normal. If airflow remains weak, or the system continues to freeze, short-cycle, or cool poorly, contact a qualified HVAC professional.
Fix 2: Reset a Tripped Circuit Breaker
If your AC won’t turn on, start by checking whether the system has power and whether the dedicated breaker has tripped. A breaker may trip because of an electrical overload, short circuit, equipment fault or another electrical issue.
You can reset the breaker once if the panel and breaker appear undamaged. Your air conditioner may then take several minutes to restart if the system has a built-in compressor protection or time-delay feature. If the breaker trips again, stop and have the system inspected rather than repeatedly resetting it.
How to Reset the AC Circuit Breaker:
- Check the panel first. Do not touch the panel if you notice a burning smell, scorch marks, buzzing, exposed wiring, excessive heat or visible damage. Contact a qualified electrical professional.
- Locate the AC breaker. It may be labelled “AC,” “Air Conditioner” or “HVAC.”
- If the breaker is tripped, move it fully to the OFF position first.
- Move it firmly to ON.
- Allow the system to restart. Follow the manufacturer’s recommended restart procedure and allow any built-in compressor time delay to complete before determining whether the AC is operating normally.
Important:
If the breaker trips again, do not reset it repeatedly. Have the system inspected by a qualified HVAC professional and, if an electrical fault is suspected, a Licensed Electrical Contractor. Repeatedly resetting a breaker can be unsafe when an underlying electrical fault is present. For more signs that indicate you may need professional service, see 8 warning signs you need AC repair services.
Fix 3: Thaw a Frozen Evaporator Coil
If your AC is blowing warm air or barely any air, and you see ice on the copper refrigerant lines or inside the air handler, the evaporator coil may be frozen. While a frozen coil can usually be thawed safely, thawing only addresses the immediate symptom. The underlying cause, such as restricted airflow or a refrigerant problem, should be identified and corrected to prevent the coil from freezing again.
How to Safely Thaw a Frozen Evaporator Coil
- Turn cooling OFF at the thermostat. Do not continue running the AC while the coil is frozen.
- With cooling turned off, you can set the thermostat fan to ON to circulate indoor air and help the coil thaw, provided your system operates normally in fan-only mode.
- As the ice melts, check for water around the indoor unit or condensate drain. If water is pooling or the drain appears blocked, turn the system off and contact a qualified HVAC professional.
- Allow the ice to melt completely. Do not use a heat gun, hair dryer, or other direct heat source to speed up the process.
- Once the coil has fully thawed, check and replace a dirty air filter if necessary.
- Restart the system and monitor it for signs of refreezing.
Important: If replacing a dirty filter does not resolve the problem, or the coil freezes again after restarting, the system needs professional diagnosis. Possible causes include restricted airflow, a dirty evaporator coil, blower problems, or low refrigerant caused by a leak. Refrigerant-related repairs and internal component diagnosis require appropriate tools and qualified service.
Fix 4: Check and Clear an Accessible Condensate Drain Blockage
A blocked condensate drain can cause water to back up around the indoor unit and, on systems equipped with an overflow safety switch, shut the AC down. If the drain outlet is readily accessible and the blockage is in the accessible section of the drain line, a homeowner may be able to clear it with a wet-dry vacuum. If you are unsure of the drain configuration, see standing water around the indoor unit, or cannot safely access the drain, contact a qualified HVAC professional.
If your system has been leaking or shutting down unexpectedly, our detailed post on why your air conditioner is leaking water covers additional causes beyond a blocked drain.
What you’ll need: Wet-dry vacuum and a rag to help create a seal around the drain outlet.
How to Clear a Clogged AC Condensate Drain
- Turn off the AC at the thermostat before working on the condensate drain.
- Locate the accessible condensate drain outlet where the pipe exits the home.
- Place the wet-dry vacuum hose over the drain outlet and use a rag to create a seal around the connection.
- Run the vacuum according to the vacuum manufacturer’s instructions to remove the blockage. Do not disconnect the drainpipe or remove panels from the indoor unit.
- If your system has a visible condensate drain cleanout or access port that is intended for homeowner maintenance, check it according to the equipment manufacturer’s instructions. Do not open sealed equipment panels.
- Check the area around the indoor unit for standing water or signs of leakage. If water is pooling, the drain remains blocked, or the system continues to shut down after the accessible blockage has been cleared, contact a qualified HVAC professional.
- Restore power to the system and confirm that the AC operates normally and that condensate is draining properly.
Important: A clogged drain is not the only possible cause of water around an indoor AC unit. A damaged condensate pan, blocked internal drain, frozen evaporator coil, installation issue or other fault may require professional diagnosis. Do not continue operating the system if water is leaking into the surrounding area or causing property damage.
Fix 5: Clean Around the Outdoor Condenser Unit
The condenser unit releases heat from your home to the outdoors and needs adequate airflow to operate efficiently. Debris and vegetation around the unit can restrict airflow, reduce efficiency and increase the system’s operating load. Clearing debris and vegetation around the outdoor unit is generally safe for homeowners, but cleaning the internal coil or working on electrical or refrigerant components should be left to a qualified HVAC professional.
Safe DIY tasks
- Turn off the outdoor unit at the disconnect before cleaning. Do not open electrical panels, remove electrical covers or work on the unit’s wiring.
- Remove leaves, grass clippings and other debris from around the outdoor unit and from accessible exterior surfaces. Do not reach through the grille or remove the condenser housing.
- Trim vegetation to maintain at least 610 mm (2 ft) of clearance around the unit, unless your manufacturer’s instructions specify a different requirement.
- If a few exterior condenser fins are lightly bent, you can carefully straighten them with a fin comb while the system is fully powered off. Avoid excessive pressure and stop if the fins or coil are significantly damaged.
Not safe to DIY: Do not work on the refrigerant lines, electrical components or internal parts of the condenser. These tasks require a qualified HVAC professional. Learn more about AC maintenance
If the condenser is heavily soiled, the AC is short cycling, or cooling performance remains poor after clearing the surrounding area, have the system professionally inspected. Several different problems can cause these symptoms.
Fix 6: Replace Thermostat Batteries
If your thermostat uses replaceable batteries, depleted batteries can cause a blank or dim display and may prevent the thermostat from communicating properly with your AC system.
If the thermostat screen is blank or dim, or the system does not respond to temperature changes, replace the batteries with the type specified by the thermostat manufacturer.
If the display remains blank after replacing the batteries, do not attempt to troubleshoot wiring or other electrical components yourself. Contact a qualified HVAC professional.
The DIY Line: What Should Be Left to a Professional
Knowing how to fix your AC yourself also means knowing when to stop. Tasks involving refrigerants, high-voltage electrical components or complex diagnostics should be left to a qualified HVAC professional, as incorrect repairs can cause further equipment damage or create serious safety hazards. In Ontario, refrigerant handling and servicing are subject to applicable regulatory requirements, and work involving regulated refrigerants should be performed by appropriately qualified personnel.
| Task | Why it needs a professional |
|---|---|
| Refrigerant leak or low refrigerant | Requires leak diagnosis, refrigerant recovery and servicing by appropriately qualified personnel |
| Capacitor replacement | Capacitors can retain a dangerous electrical charge even after power is disconnected |
| Contactor replacement | Involves high-voltage electrical components and requires appropriate electrical knowledge |
| Compressor diagnosis | Requires specialized electrical and mechanical testing |
| Control board diagnosis or replacement | Requires specialized electrical and system diagnostics |
| Wiring repairs | Creates potential shock, short-circuit and fire hazards |
| Refrigerant line repair | Requires refrigerant recovery, leak repair and proper system recharging |
If your system has any of the issues above, or if a DIY fix hasn’t resolved the problem, LG Home Comfort’s licensed HVAC technicians are available across Ontario. For AC repair or service call at 1-866-438-5442.
For a broader look at all common AC problems and their fixes, see our complete guide on what to do if your AC stops working in Ontario.
Conclusion
Many common air conditioner problems do not require a technician, and tasks like replacing a dirty filter, checking a tripped breaker, replacing thermostat batteries, clearing minor debris, or thawing a frozen coil are reasonable to handle on your own.
However, the important part is knowing where to stop: if your system continues to freeze, repeatedly trips a breaker, or shows signs of a refrigerant leak, capacitor failure, or electrical component issue, further DIY attempts can create safety risks or cause additional damage, so these issues should be left to qualified professionals.
Frequently Asked Questions
01 How much does a new central air conditioner cost in Ontario?
02 What size AC do I need for my Ontario home?
03 Are there government rebates for new air conditioners in Ontario?
04 How long does a central AC last, and is it better to repair or replace?
05 Does the brand of the AC affect the installation cost?
06 Is a permit required for an AC or heat pump installation in Ontario?
07 Should I replace my furnace at the same time as my AC?
08 How much does central AC cost to run monthly, and can I finance it?
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