The first genuinely hot week of the year is when everyone discovers their air conditioning has a problem, and it is also the week every HVAC company in the Lower Mainland is fully booked. Which makes the ten minutes of checks below unusually worth doing.
1. The filter, again
Same mechanism as with heating, different failure. A restricted filter starves the indoor coil of airflow. With too little warm air passing over it, the coil gets too cold and freezes into a block of ice — and a frozen coil moves no heat at all.
Pull the filter. If it is grey and matted, that is very likely your problem.
If the coil is already frozen, turn the cooling off but leave the fan running. It needs several hours to thaw, and running the compressor against a frozen coil damages it. Replace the filter while it thaws.
2. The outdoor unit
Go outside and look at the condenser.
Is it running? Fan spinning, compressor humming. If the indoor blower runs but the outdoor unit is completely dead, check whether there is a separate breaker or disconnect for it — there usually is, in a small box on the wall near the unit.
Is it clear? Cottonwood seed, grass clippings, leaves and blackberry growth pack into the fins and stop it rejecting heat. It needs clear air on all sides and above. Hosing the fins gently from the inside out, with the power off, does a surprising amount of good.
Is anything growing into it? In this climate, plants against a condenser is the normal state of affairs by August. Give it 60cm of clearance.
3. Thermostat, properly
Set to COOL, not AUTO-changeover, and the setpoint genuinely below room temperature. Fan on AUTO — same reason as with heating, ON means the blower runs between cycles pushing unconditioned air.
Then give it time. An air conditioner does not cool a house that has been baking all afternoon in fifteen minutes.
4. Windows, doors and the sun
Obvious, and worth stating because we have driven out for it.
A house that has had west-facing windows in full sun all afternoon has an enormous heat load. Blinds closed on the sun side before it gets hot does more than most people expect — often more than a thermostat adjustment.
Check no windows are open, no doors are propped, and the bathroom and kitchen extract fans are off, because they are pumping your cooled air outside.
5. Vents and returns
Walk the house. Closed supply registers in unused rooms feel like a saving; they are not, and enough of them will imbalance the system and reduce total capacity.
Check the return air grille is not behind furniture or blocked by a rug. The system needs to pull air back as much as it needs to push it out.
Stop and call if
- The coil keeps freezing after you have replaced the filter and thawed it. That usually means low refrigerant, and low refrigerant means a leak. Topping it up without finding the leak is throwing money into the air.
- There is water pooling around the indoor unit. The condensate drain is blocked.
- You hear grinding, screeching or repeated hard clicking from the outdoor unit. Turn it off.
- The breaker trips repeatedly. Do not keep resetting it. That is a fault telling you something.
The one people get wrong about refrigerant
Air conditioning does not “use up” refrigerant. It is a sealed system. If it is low, it leaked, and it will leak again.
Anyone who offers to just top it up without diagnosing the leak is selling you the same repair next summer. Ask where the leak is.
Getting ahead of it
The realistic advice is unglamorous: have it looked at in spring, not in the second week of a heat wave. Coil cleaning, refrigerant pressures, electrical connections and drain clearing take an hour and prevent most of what we see in July.
That is what the maintenance plans exist for, and it is also why the plan includes scheduled reminders — nobody spontaneously remembers to book AC service in April.
If your house was built before air conditioning was standard here, the problem may be less about the equipment and more about the building; we go into that in cooling a Lower Mainland house that was never built to be cooled.
Otherwise we do AC repair across the Lower Mainland. During a heat wave, phone early — that is not a sales line, it is just how the day fills up. The rest of what we do on air conditioning is worth a look if you are weighing up a replacement rather than a repair.