Why Is My Air Conditioner Not Cooling? Common Causes & Fixes

Is your AC running but not cooling?

When your air conditioner is running but the house still feels warm, you have a problem! It might be a dirty filter, incorrect thermostat setting, or perhaps the outdoor unit is blocked. The same kind of thing can apply to a heat pump when it’s in cooling mood.

If you check all those and they don’t restore your cool air (or, if you see ice or smell burning!), you’ll want to call a licensed HVAC technician.

But First, Check These Quick Fixes Yourself

Before booking a repair, work through this checklist:

• Check the thermostat. Set it to COOL and several degrees below the room temperature. Set the fan to AUTO, not ON, which can circulate uncooled air between cycles. Replace weak batteries!
• Inspect the air filter. A dirty filter restricts airflow and is one of the most common reasons for an air conditioner not cooling. Check it monthly and change or clean it every 30–90 days, depending on pets, smoke, dust, and system use.
• Check the breaker once. Reset a tripped breaker once. If it trips again, stop and call a technician.
• Open supply vents. Make sure vents are open and not blocked by furniture, rugs, curtains, or boxes.
• Inspect the outdoor unit. Turn the system off, then remove loose leaves, grass clippings, and debris from around it. Coastal pollen and vegetation can also restrict airflow. Leave about 60 centimetres of clearance around the unit.

*Do not remove panels, touch wiring, or pressure-wash the coil.

Your AC Is Running but Blowing Warm Air—Here’s Why

After all the above checks are said and done, and you still have warm air blowing, the cause may be inside the system. Here’s a few of the common reasons why.

Low or Leaking Refrigerant

Refrigerant works by absorbing heat indoors and releasing it outside. Air conditioners don’t normally “use up” refrigerant, so if you have a low level, it usually means there’s a leak somewhere. Weak cooling, hissing, an iced-up refrigerant line, or unusually long run times are all indicators of this.

This is not a DIY repair. Leak testing, charging, refrigerant handling and related work must be completed by a certified technician in Canada. If you suspect any of the above, we can help.

Frozen Evaporator Coil

Restricted airflow from clogged filters, blocked ducts, or blower issues can freeze your evaporator coil. The evaporator coil is the cold indoor component that removes heat from the air. If the coil gets too cold (from one of the causes above), it’ll cause moisture to freeze on it. Low refrigerant can also cause the evaporator coil to freeze. 

If you see ice, switch the system from COOL to OFF. Allow it to thaw completely. If you continue to run a frozen system, it can cause damage to the compressor. Replace dirty filters and check that the vents are open, but be sure to call a technician if the ice returns.

Dirty Condenser Coils

There’s an outdoor condenser coil that releases heat from your home, but if there’s buildup around it, the AC may run continuously without cooling properly. Clear any loose debris from around the cabinet, but leave deep cleaning, panel removal and fan problems to a professional.

The AC Turns On but the House Never Cools Down

Does your AC produce cool air but it can’t cool the whole home? This may be the result of an undersized system.

A system too small for the home it’s in can run constantly because it doesn’t have the capacity for the space it’s responsible for. If your ducts are poorly insulated, disconnected, leaky or crushed, they may be seeping out the cool air before it reaches your rooms. Also, on hot days, the sun, open windows, poor insulation, and oven use may create more heat than the system can remove.

Because Vancouver Island summers are trending hotter, equipment sized years ago might be struggling to keep up with new temperature extremes. This effect can become amplified as the system ages and loses capacity.

Signs You Should Call a Licensed HVAC Technician

You’ll want to stop troubleshooting and arrange for a professional AC repair when you notice any of the following:

• Ice returning after the system has thawed
• Hissing or signs of a refrigerant leak
• Warm air after completing all basic checks
• A breaker that repeatedly trips
• Rapid starting and stopping, called short-cycling
• A burning or electrical smell
• A compressor or outdoor fan that will not start
• Water leaking near electrical components

Turn the system off if you smell burning or see smoke. Refrigerant, internal electrical, compressor, and sealed-system work require professional training and certification. Book with us today.

Keep It From Happening Again

A few simple maintenance habits can prevent many of the no-cooling-type calls we’ve looked at in this article:

• Check the filter monthly and replace it every 30–90 days.
• Keep plants, leaves, and clippings away from the outdoor unit.
• Keep supply and return vents open.
• Schedule annual AC maintenance before peak summer heat.

*A tune-up checks airflow, electrical parts, coils, drains, refrigerant performance, and overall system condition before summer hits.

Frequently Asked Questions

Why is my AC running but not blowing cold air?

Common causes can include an incorrect thermostat setting, dirty filter, blocked outdoor unit, frozen coil, low refrigerant, electrical fault, or a failing compressor.

Can a dirty air filter stop my AC from cooling?

Yes! A clogged filter will restrict airflow, reduce cooling capacity, and may contribute to a frozen indoor coil.

Why is my air conditioner freezing up?

Restricted airflow and low refrigerant are the common causes. Turn your system off, let the ice thaw, check the filter and vents, and call a technician if it freezes again.

How do I know if my AC is low on refrigerant?

Possible signs include weak cooling, long run times, hissing, and ice on the coil or refrigerant line. Only a certified technician can confirm the cause, repair a leak, and handle refrigerant.

When Should I Call an HVAC Technician Instead of Fixing It Myself?

Call when the thermostat, filter, breaker, vent, and outdoor-clearance checks do not work, or when you notice recurring ice, electrical issues, short-cycling, burning smells, or possible refrigerant problems.

Still Stuck With Warm Air?

Ran through the checklist and still stuck with warm air? A frozen coil, low refrigerant, or a struggling compressor needs a licensed set of hands! 

Archie Johnstone’s HVAC technicians serve homeowners across Vancouver Island. Book a service call and we’ll have your home cool again fast!

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