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How to Fix 14 of the Most Common Air Conditioner Problems
How to Fix 14 of the Most Common Air Conditioner Problems
Air conditioners can run into many different problems, but diagnosing them doesn’t have to be complicated. You don’t need to be an expert in every part — just knowing the common signs and where to start checking can save you time and stress.
In this guide, we’ll go through the most common air conditioner problems one by one, so you can understand what’s going on with your system and bring back the cool comfort to your home.
1. Noisy Air Conditioner
Why Your AC Is Making Strange Sounds
If your air conditioner is making unusual noises, it’s a sign that something’s not right. Instead of panicking or calling a technician right away, try to figure out what kind of sound it is — this gives you a big clue about the issue.
| Sound | Possible Cause |
| Banging | Loose or broken part (like a piston or rod) |
| Buzzing | Loose wiring, dirty filter, or frozen coil |
| Clicking (repeated) | Faulty thermostat or electrical issue |
| Hissing | Refrigerant leak or high internal pressure |
| Rattling | Loose screws or debris inside the unit |
Quick Fix Tips:
- Locate where the sound is coming from — indoor unit, outdoor unit, or ducts.
- Clear away any debris from the outdoor unit fan area.
- Make sure fan blades are not bent or hitting the sides.
- If something is rattling, place a bit of soft padding to stop vibration temporarily until a technician checks it.
2. AC Freezing Up
Why Even a New AC Can Freeze
Yes, even a brand-new AC can freeze if it’s not working correctly. The main reasons are poor airflow (dirty filter), low refrigerant, running for long hours without a break, or thermostat set too low.
Quick Fix Tips:
- Turn off the AC and run just the fan to melt the ice.
- Clean or replace the air filter.
- Open all vents and remove anything blocking airflow.
- If it keeps freezing again, call a technician to check refrigerant levels or leaks.
3. AC Not Turning On
What to Do When Your AC Won’t Start
If your AC won’t turn on at all, it might be something simple like a tripped breaker or dead thermostat batteries — or a safety shutdown caused by airflow problems.
Quick Fix Tips:
- Reset the circuit breaker if it’s tripped.
- Replace thermostat batteries.
- Make sure the air filter is clean and vents are open.
- In Canada, summer storms are common — use a surge protector to protect your AC from power surges.
4. AC Fuse Keeps Blowing
Why the Fuse Keeps Tripping
Loose wiring, wrong fuse size, or a clogged filter can overload the system and blow the fuse. Even vibrations from the AC can loosen electrical terminals over time.
Quick Fix Tips:
- Replace a dirty air filter.
- Check for damaged or exposed wires.
- Inspect the capacitor — if it’s weak, it draws more power and blows fuses.
- Clean the condenser coil.
- Tighten loose wire connections (only if you are confident and safe doing it).
If the fuse keeps blowing again and again, it’s likely an electrical issue that needs a professional.
5. Air Conditioner Not Turning Off
Why Your AC Runs Nonstop
If your air conditioner keeps running without stopping, it can be due to a stuck relay, thermostat problem, or poor airflow from a dirty filter, frozen coil, or low refrigerant.
Quick Fix Tips:
- Set thermostat mode to “AUTO” not “ON.”
- Clean or replace the air filter.
- Inspect the outdoor unit — a stuck contactor can keep it running.
- Reset the system by turning off the power for a few minutes.
6. Air Conditioner Lights Are Blinking
What Blinking Lights Mean
Blinking lights on an AC usually mean the system is trying to warn you about a problem. Some brands even use blinking codes to show exact issues.
Quick Fix Tips:
- Check your AC’s user manual for the meaning of the blinking pattern.
- If the lights keep flashing, call a technician — it might be a sensor or control board problem.
7. Air Conditioner Leaking Refrigerant
Signs of a Refrigerant Leak
A refrigerant leak lowers your AC’s cooling power and can harm the environment. Older refrigerants like R-22 damage the ozone layer, while newer ones also contribute to greenhouse gases, so handling them needs proper care.
Common Signs:
- Weak or warm airflow
- Ice on coils or refrigerant lines
- Hissing or bubbling sounds
- AC runs constantly
- Higher electricity bills
- Unusual indoor humidity
- Chemical smell near the unit
What to Do:
- Turn off the AC to avoid damaging the compressor.
- Call a certified HVAC technician to find and repair the leak, then recharge the refrigerant safely.
Never try DIY refrigerant refills — it’s risky and illegal without proper certification.
8. AC Blowing Hot Air
Why Cold Air Turns into Hot Air
When your air conditioner starts blowing hot air instead of cooling, something’s definitely wrong. The common reasons are low refrigerant, a dirty air filter blocking airflow, or an issue with the outdoor unit. Sometimes it’s as simple as the thermostat accidentally set to “heat.”
Quick Fix Tips:
- Set your thermostat to “cool” and lower the temperature setting.
- Clean or replace the air filter.
- Make sure the outdoor unit is running normally.
- If it still blows warm air, call a technician to check for a refrigerant leak or compressor problem.
9. Water Leaking from AC
When Water Leaks Are Normal—and When They’re Not
Some water dripping outside the unit is normal because of condensation, especially on hot or humid days. But water leaking inside your home means something’s wrong—usually a clogged drain line, dirty filter, or a frozen coil melting.
Quick Fix Tips:
- Turn off the AC and check the air filter. Replace it if it’s dirty.
- Pour warm water or vinegar down the drain line to clear blockages.
- If water keeps appearing indoors, call a technician to inspect for frozen coils or a damaged drain pan.
10. Bad Smells from the Air Conditioner
What Different AC Smells Mean
Unusual smells from your AC can be a warning sign. They can come from bacteria, mould, electrical issues, or even a refrigerant leak.
| Smell | Possible Cause |
| Musty / Mouldy | Mould or mildew in the drain pan, filter, or ducts |
| Dirty Socks | Bacteria on the evaporator coil |
| Burning | Overheating motor or electrical issue |
| Rotten Eggs | Dead animal in ducts or near the unit |
| Sweet / Chemical | Refrigerant leak (R-22 or R-410A) |
| Vinegar-like | Clogged drain or bacteria growth |
| Exhaust Fumes | Leaking refrigerant or compressor oil |
Quick Fix Tips:
- Turn off the AC and replace a dirty or smelly air filter.
- Pour a vinegar + warm water mix down the drain line to kill bacteria.
- If the smell is musty or like dirty socks, clean the evaporator coil.
- If odours continue, stop using the AC and call a technician quickly.
11. AC Turning On and Off Repeatedly (Short Cycling)
Why Your AC Keeps Starting and Stopping
Short cycling is when your AC keeps turning on and off without cooling properly. It puts a lot of strain on the system. The main causes are a clogged filter, low refrigerant, or a thermostat placed in direct sunlight.
Quick Fix Tips:
- Replace the air filter.
- Move anything that’s affecting airflow near the thermostat.
- If it continues, ask a technician to check refrigerant levels or see if the AC is oversized for your home.
12. AC Ducts Leaking
How Duct Leaks Waste Cooling
Central AC systems push cool air through ducts to reach rooms. If your ducts are leaking, cool air escapes into unused spaces like attics or walls, wasting energy. Many older Canadian homes have poorly sealed ducts, which can lose up to 30% of cooling power.
Common Causes:
- Age and wear
- Damage during renovations
- Pests tearing or dislodging ducts
- Poor installation
- Pressure imbalances
Quick Fix Tips:
- Seal accessible duct joints using UL 181-rated foil tape or duct mastic (not regular cloth duct tape).
- Hire a professional for duct testing and sealing. Some use Aeroseal technology that seals leaks from the inside.
13. Air Conditioner Takes Too Long to Cool
If your AC is running but takes forever to bring down the temperature, it’s likely working harder than it should. This can happen for several reasons — the system might be undersized for your home, have a clogged air filter, or dirty coils. Extremely hot days, poor insulation, leaky ducts, or open windows letting cool air escape can also slow things down.
Solution
Replace the air filter and make sure all windows and doors are closed. Shade the outdoor unit if it’s in direct sunlight, and check that nothing is blocking the indoor vents. If the system still cools slowly, call a technician to inspect for low refrigerant levels or dirty coils.
14. AC Bill Is Too High
If your energy bill has suddenly spiked, your AC is probably running longer and harder than necessary. This often happens due to restricted airflow, dirty components, or leaking ducts, all of which force the system to consume more power to maintain the set temperature.
Solution
- Replace the air filter every 1–2 months during cooling season
- Seal duct leaks or gaps to stop cooled air from escaping
- Use a programmable or smart thermostat to manage run times
- Keep blinds or curtains closed during the hottest part of the day
- Clean the outdoor condenser unit to prevent dust buildup
- Schedule an annual AC tune-up to keep it running efficiently
- Avoid setting the thermostat too low — it won’t cool faster, only run longer
Keep Your AC in Top Shape — Call a Trusted Local Contractor
Even the best air conditioners need occasional care to run at peak performance. It’s not about doing anything wrong—most AC systems simply benefit from a quick tune-up before the cooling season begins.
A routine check by a qualified technician can boost efficiency, reduce energy bills, and extend your system’s lifespan.
At ACPrices.com, we make it easy to connect with trusted, fully vetted HVAC professionals across Canada. Compare free AC repair and maintenance quotes from top-rated local contractors and find the right expert to keep your home cool and comfortable all summer long.
