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AC Not Cooling? Quick Checklist Before You Call
It’s 30°C outside and your home feels like a sauna — but don’t panic yet.
When your AC is running but not cooling, it’s usually something simple: a dirty filter, a tripped breaker, or blocked outdoor airflow.
This quick checklist walks Calgary homeowners through the easy, safe steps to troubleshoot before booking a service call. You might fix it yourself — or at least know exactly what to tell your tech when they arrive.
Step 1: Check the Thermostat (the Boss)
It sounds obvious, but thermostats are sneaky troublemakers.
1
Is it set to COOL? (Not HEAT, not OFF, not FAN.)
2
Is the temperature set below the current room temp?
3
If it's battery powered, are the batteries fresh?
4
For smart thermostats: did Wi-Fi or software updates mess with settings?

Pro Tip: Put it on COOL and set it at least 3–4°C lower than the room to ensure it kicks in.
Step 2: Air Filter – The #1 Culprit
A dirty filter is like putting a pillow over your AC's mouth. No airflow = no cooling.
  • Pull it out. If it looks gray, clogged, or furry → replace it.
  • Standard 1" filters should be swapped every 30–60 days in summer.
  • Most "AC not cooling" calls in July start with a $10 filter problem.
Step 3: Indoor Unit — Is the Blower Running?
Head to your furnace/air handler.
• Do you hear the blower fan running?
If not, check:
  • The furnace switch (looks like a light switch nearby)
  • The breaker — reset once if it's tripped
If the blower isn't moving air, your AC can't cool anything.
Step 4: Outdoor Unit — Is It Running?
Step outside and listen.
Is the outdoor fan spinning?
Do you hear the compressor humming?
If it's dead quiet, check the breaker or disconnect switch near the unit
If the fan hums but doesn't spin, the capacitor or motor may be toast — call a pro. Don't stick your hand in the blades.
Step 5: Airflow Inside the House
Even if the system is running, bad airflow = poor cooling.
Check Vents
Walk around and check vents. Are they open and blowing?
Look for Blocked Returns
Behind couches, rugs, or furniture
Vent Management
Close only a few vents at most — never more than 10–15%
Step 6: Ice, Ice, Baby (Coils Freezing)
If you see frost or ice on the copper lines or indoor coil:
Turn the system OFF immediately
Run the FAN only to thaw it
Causes: dirty filter (again), low refrigerant, or airflow restriction.
Low refrigerant means a leak → requires a licensed tech.
Step 7: Outside Obstructions
Your outdoor condenser needs to breathe.
  • Clear leaves, weeds, or fences within 2 feet.
  • Don't stack junk or lean wood/ladders against it.
  • Rinse the coil gently with a garden hose (never pressure wash).
Step 8: When to Call a Pro
After you've done the basics, it's time to bring in a technician if:
1
Power Issues
The outdoor unit won't start despite power checks
2
Warm Air
The indoor blower runs but air is warm
3
Persistent Ice
Ice keeps returning on lines or coil
4
Strange Sounds
You hear grinding, squealing, or loud buzzing
5
Refrigerant Issues
You suspect a refrigerant problem
Preventive Tips & Quick FAQs
Stay Ahead Next Summer
  • Change filters regularly.
  • Schedule annual AC tune-ups (clean coils, check refrigerant, test controls).
  • Keep landscaping trimmed around outdoor units.
  • Run ceiling fans to ease AC load on extreme days.
Quick FAQs
Q: Why does my AC run but not cool the house?
A: Usually a dirty filter, frozen coil, or outdoor unit not running.
Q: Can I hose off my outdoor unit?
A: Yes, gently rinse from top down. Do not use pressure washers.
Q: How often should I service my AC?
A: Once per year — ideally in spring before the first heat wave.
Conclusion
Your AC has a few weak spots, but most are easy to check. Filters, airflow, and power are common culprits you can solve in minutes. If the system still isn't cooling after this checklist, it's time to call in the pros.
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