Quick answer
Deal with the house and the people in it first, then the equipment. Shade the windows, move sleeping downstairs, and check on anyone elderly or unwell. Then look at the two things that fail most often — a tripped breaker and a frozen indoor coil — before you book service. Heat stroke, with confusion or fainting, is a 911 call.
If your AC fails during a heat wave, work on the house and the people in it before you work on the machine. A stalled compressor is an inconvenience; an upstairs bedroom that never drops below 30 °C for three nights running is a health problem, and it is the second one that puts people in hospital. This is the order we give homeowners when every contractor in Halton is booked solid.
Make the house liveable tonight
- Close blinds and curtains on the south and west sides by mid-morning. Blocking sunlight before it lands beats trying to cool the room after.
- Move sleeping downstairs. Hot air stacks, so a mattress on a basement floor beats a second storey under a hot roof.
- Wait until the outdoor air is genuinely cooler than the indoor air before you open up. Near the water in Bronte, Aldershot and Burlington's south end the breeze off Lake Ontario does that first; up in Tyandaga and above Dundas Street it comes later.
- Put a box fan in an upstairs window blowing out, with a window open downstairs on the shaded side. That exhausts the hottest air instead of just stirring it.
- Skip the oven, the dryer and long hot showers, run the exhaust fans in the evening, and drink water on a schedule rather than waiting for thirst. A cool shower moves core temperature more than a fan does.
Who is at real risk, and where the 911 line is
Infants, adults over 65, anyone with heart, lung or kidney conditions, outdoor workers and people on medications that affect fluid balance are the ones who get hurt in a heat event — a pharmacist can tell you in half a minute whether a prescription belongs on that list. Check on them in person twice a day. Never leave a child or a pet in a parked car.
Heat exhaustion looks like heavy sweating, weakness, nausea, headache and cool clammy skin, and it improves in a cool room with water and the legs raised. Heat stroke looks different: hot skin that may be dry, a temperature that keeps climbing, confusion, slurred speech, fainting or a seizure. Call 911 immediately and cool the person with water and moving air while you wait. Environment and Climate Change Canada issues heat warnings for Halton and Hamilton when daytime highs and overnight lows both stay elevated for consecutive days, and the overnight figure is the one that matters — a house that never gets a cool night has nowhere to dump the heat it stored.
Three checks before you book, and one thing not to do
- The breaker. Central AC runs off a double-pole 240-volt breaker in the panel plus a disconnect box beside the outdoor unit. Reset a tripped breaker once. If it trips again, leave it off — repeated resets on a shorted compressor are how a bad afternoon becomes a fire. See why an AC trips the breaker.
- Ice. If the indoor coil is a block of ice or the copper line entering the house is frosted, set the thermostat to OFF and the fan to ON and give it a few hours to thaw. Change the filter while you wait. A frozen coil means airflow or refrigerant is wrong, and running it iced up destroys compressors.
- The float switch. A plugged condensate drain fills the pan under the coil, and a small float switch shuts the system down on purpose. It is one of the most common no-cooling calls in July.
- Do not top up refrigerant from a hardware-store can. Systems do not consume refrigerant, so if it is low it leaked, and overcharging turns a small repair into a compressor bill.
What the repair usually is, and why the queue is long
Most heat-wave failures are small electrical parts that were already marginal in May and finally quit on the first 33 °C afternoon. A capacitor or contactor is the classic at $150–$350, replaced on the first visit from a stocked truck. Across the board most AC repairs run $150–$800 depending on the part, and the diagnostic visit is $90–$150, folded into the repair if you go ahead. ZK Mechanical adds no overtime, weekend or holiday surcharge, which matters when the failure lands on the Saturday of a long weekend. The full breakdown is in what AC repair costs in the GTA.
The backlog is real. Every contractor from Aldershot to Stoney Creek takes the same flood of calls inside the same 48 hours, so triage decides the order: a total failure in a house with an infant or a frail elderly resident moves ahead of a system that is merely cooling poorly. Say so when you call.
Heat-wave questions we get every July
- Should the fan be on ON instead of AUTO? For a few hours to thaw a frozen coil, yes. Otherwise leave it on AUTO, because a continuously running fan re-evaporates moisture off the coil and makes the house feel muggier.
- Will a portable unit hold a bedroom? A single-hose portable takes the edge off one small room if the exhaust hose is sealed properly into the window. It cannot cool a whole floor.
- It runs but barely cools. Check the filter, then the outdoor coil — a condenser packed with cottonwood fluff cannot reject heat. With the power off at the disconnect, rinsing that coil from the inside outward with a garden hose is homeowner-safe.
- Is this system worth repairing? Past about 12 years, with a compressor failure, replacement usually wins, especially with the refrigerant changeover under way — see is it worth repairing a 10-year-old AC.
- Can I get same-day help? Sometimes, and calling early improves the odds, but nobody can honestly promise a time during a heat warning when every phone in Halton rings at once. Tell us if anyone in the house is at risk and we triage on that.
ZK Mechanical is owner-operated out of North Service Road in Burlington and runs a 24/7 line with no after-hours premium. For air conditioner repair and installation, or AC service in Burlington, call (647) 801-1252 or book a visit online.