AC not cooling in Calgary quick checks and next steps

When your AC is running but your home still feels warm, it can get uncomfortable fast. In Calgary, hot days may not last as long as in other places, but when a heat wave hits you want your system to work. This guide covers quick checks you can do at home, the most common reasons an air conditioner stops cooling, and the signs you should book service.

Quick safety note before you start

Air conditioning systems use electricity and moving parts. Do not open sealed panels or try to handle wiring if you are not trained. Never try to add refrigerant yourself. If you smell burning, see smoke, or hear loud electrical buzzing, turn the system off and call a professional.

First confirm the problem

Start by checking if your system is truly not cooling, or if airflow is the main issue.

• Stand at a supply vent and feel the air. Is it weak, or strong but not cool.
• Check a few rooms. If one room is fine and others are warm, airflow and duct balance may be the issue.
• Look at your thermostat temperature. If the room temperature is not dropping after 30 to 60 minutes, keep going with the checks below.

Step one check thermostat settings

Thermostat settings cause a lot of “AC not cooling” calls.

Set it to cool and lower the set point

• Set the mode to Cool.
• Lower the set temperature by 2 to 3 degrees and wait a few minutes.
• If you use a schedule, switch to a temporary hold for testing.

Set the fan to auto

Fan on can run the blower all the time. That can make air feel less cool between cycles. Auto is best for most homes.

Check batteries and connection

If your thermostat uses batteries, replace them. If it is a smart thermostat, confirm it still has power and WiFi is not causing a control issue. If the screen is blank, you may have a power problem to the system.

Step two check the breaker and shutoff switches

Your AC system usually has two power points. One for the indoor unit and one for the outdoor unit.

Check your electrical panel

Look for a breaker labeled AC, Air conditioner, or Condenser. If it is tripped, reset it once. If it trips again, stop and book service.

Check the outdoor disconnect

Many homes have a small shutoff box near the outdoor unit. If it was turned off for yard work or repairs, the AC will not cool. If you are not sure, do not force anything. A technician can confirm it safely.

Step three replace the air filter

A clogged filter can reduce airflow so much that your AC struggles to cool. It can also cause the indoor coil to get too cold and freeze.

Signs of a dirty filter

• Weak airflow at vents
• Some rooms are much warmer than others
• AC runs for a long time with little change
• You see more dust than normal

What to do

• Turn the system off at the thermostat.
• Replace the filter with the same size.
• Turn the system back on and test again for 30 minutes.

Step four check vents and return air

Cooling depends on good airflow.

• Make sure supply vents are open and not blocked by rugs or furniture.
• Make sure return vents are not blocked.
• If you close vents in unused rooms, open them back up for testing.

If your home has multiple floors, warm air rises. Upstairs may feel warmer even when the system is working. Good airflow and smart thermostat settings can help, but some homes need zoning or balancing work.

Step five check the outdoor unit

Your outdoor unit needs clear airflow to remove heat from your home.

Clear space around it

• Remove leaves, grass clippings, and debris around the unit.
• Keep shrubs trimmed back so air can move.
• Do not cover the unit while it is running.

Look for obvious signs

• Is the fan spinning.
• Do you hear the unit running.
• Is there ice on the lines or coil.

Is the coil dirty

A very dirty outdoor coil can reduce cooling. If the coil looks packed with debris, a professional cleaning is a good idea. Avoid bending fins or spraying harsh chemicals. A technician can clean it the right way without damage.

Step six check for ice

Ice is a common reason an AC stops cooling. When ice forms, airflow drops and the system cannot move enough air to cool the home.

Where you might see ice

• On the copper line near the outdoor unit
• On the indoor coil area near the furnace or air handler
• On the outdoor unit coil

What to do if you see ice

Turn the system off at the thermostat. Let the ice melt. You can set the fan to auto and wait, or set the fan to on for a short time to help move air and speed melting. Do not chip ice off. Once it melts, replace the filter and check vents. If icing comes back, book service. Ice can be caused by low airflow, low refrigerant, or a mechanical issue.

Why your AC may be running but not cooling

After the quick checks above, the cause is often one of the issues below. Some are simple, some need a technician.

Low airflow

Low airflow can come from a clogged filter, blocked return vents, closed registers, or a blower issue. When airflow is low, the system cannot carry cool air through the home. It can also cause freezing.

Dirty indoor coil

The indoor coil removes heat from your air. If it is dirty, it cannot do that well. This can lead to long run times, weak cooling, and icing. Coil cleaning is usually a technician job.

Dirty outdoor coil

The outdoor coil releases heat outside. If it is dirty or blocked, cooling drops. You may notice the system runs but the home stays warm.

Refrigerant leak or low refrigerant

Refrigerant does not get used up. If it is low, there is often a leak. Signs can include icing, longer run times, and poor cooling. Refrigerant work needs trained service and proper tools.

Capacitor or contactor problems

These electrical parts help the system start and run. When they fail, the outdoor fan or compressor may not run right, or may not start at all. This is a common repair, but it should be handled by a technician.

Condenser fan issues

If the outdoor fan is not spinning, the unit cannot remove heat. You may hear the system hum, but cooling will be poor or gone. Turn the system off and book service.

Compressor issues

The compressor is a major part of the outdoor unit. If it is not working, cooling may stop. A technician will test the system to confirm the cause and talk through repair or replacement options.

Duct leaks or duct design problems

In some homes, cool air is lost in the ductwork or does not reach the rooms that need it most. Leaks, poor balancing, and long duct runs can reduce comfort. This often shows up as hot rooms upstairs and cool rooms downstairs.

Thermostat location and heat sources

If a thermostat is in direct sun or near a heat source, it can read warmer than the rest of the home and cause odd cycles. Curtains, lamps, and kitchen heat can affect readings.

Simple tips that help cooling in Calgary homes

These tips can help your system feel more effective, even when it is working normally.

Use your blinds during peak sun

Close blinds on the sunny side of the home in the afternoon. This reduces heat load and helps the AC catch up.

Run bathroom fans after showers

Humidity makes a home feel warmer. Venting moisture helps comfort.

Replace filters on schedule

In summer, check filters more often. A clean filter can help airflow and reduce icing risk.

Keep doors open for better airflow

In many homes, closed doors can reduce return airflow and make some rooms warm. Test with doors open to see if it improves comfort.

Set realistic temperature targets

On very hot days, it may take time to cool a home, especially if it heated up during the day. A steady setting often works better than big swings.

When to call a professional

Book service if you notice any of the items below.

• The breaker trips again after one reset
• The outdoor fan is not spinning
• You see ice more than once
• You hear loud buzzing, grinding, or clicking
• Airflow is very weak even with a new filter
• The system runs for hours with little cooling
• You see water pooling near the indoor unit

What to expect during an AC service visit

A good service visit should include a clear diagnosis and a clear price before work starts. A technician may check thermostat signals, electrical parts, airflow, coil condition, temperature readings, and system pressures. If a part is failing, they should explain the options in plain language.

FAQ AC not cooling in Calgary

Why is my AC running but not cooling

Common causes include a dirty filter, blocked vents, a dirty coil, icing, low refrigerant from a leak, or a failing electrical part in the outdoor unit. Start with thermostat and airflow checks, then book service if it does not improve.

Should I turn my AC off if it is not cooling

If you see ice, or if the outdoor fan is not running, turn it off and call for service. Running a system in that state can make the problem worse.

How long should it take for my home to cool

It depends on outdoor temperature, sun exposure, insulation, and how warm the home was when the system started. If the temperature does not drop at all after 60 minutes, or if it drops very slowly for hours, something may be wrong.

Can a dirty filter stop my AC from cooling

Yes. A clogged filter reduces airflow and can cause the indoor coil to freeze. Replacing the filter is one of the best first steps.

What does it mean if the AC lines are frozen

Frozen lines often point to low airflow or low refrigerant. Turn the system off, let it thaw, replace the filter, and check vents. If it freezes again, book a technician.

Is it normal for upstairs to be warmer

Often yes, since warm air rises. Good airflow, open returns, and balanced vents can help. Some homes need duct balancing, zoning, or insulation upgrades to improve upstairs comfort.

Your next step

If you worked through the checks above and your AC still is not cooling, it is time for a professional diagnosis. A technician can test airflow, electrical parts, and system performance safely, then explain the fix and the cost before work starts.