An AC that dies on a 33 degree Mississauga afternoon is part repair problem and part household-safety problem, so this page handles both in order: the one symptom that means shut it off now, the ten-minute checks that revive a real share of dead systems for free, exactly who to call for everything else, and how to keep the house livable while help is on the way. Aire One Peel’s emergency line runs 24/7 with no after-hours charge, and as with our furnace version of this guide, the honest goal is that you only need it when you actually do.

First: is this an emergency?

A dead AC has two genuine emergency modes, one electrical and one human, and they get handled before any troubleshooting. Everything else can wait ten minutes for the checks below.

The ten-minute checks before you call anyone

A real share of dead-AC calls end at one of these five checks, every one of them safe for a homeowner. Run them in order before spending a cent.

Safe homeowner checks only; anything involving the refrigerant circuit, capacitors, or wiring belongs to a certified refrigeration mechanic.

Symptom to likely cause

What the system is doing narrows what failed, and the biggest fork is simple: a running AC blowing warm air is a different problem family from a dead one, and it has its own full guide in our article on why an AC is not cooling. This table covers the dead and dying modes.

Patterns reflect common central AC failure modes; the same symptom can trace to different failures, so the on-site diagnosis governs.

Who handles what: the routing table

“Who do I call” has different answers depending on what actually failed, and in a heat wave the first row matters more than any repair. This routing applies across Mississauga and all of Peel Region.

Routing per Ontario’s trade and utility structure; outside Mississauga and Brampton the distributor differs: Hydro One for Caledon and Bolton, Milton Hydro for Milton, Halton Hills Hydro for Georgetown, Toronto Hydro for Etobicoke.

For the AC itself, the credential that matters is the refrigeration trade: in Ontario, refrigerant handling is regulated under O. Reg. 463/10 and belongs to certified 313A or 313D refrigeration and air conditioning mechanics, so ask any company you shortlist who actually touches the refrigerant circuit. The other questions worth asking at 9pm on a hot Friday are whether after-hours carries a surcharge and whether the diagnosis comes in writing with the failed part named; we answer no surcharge and yes in writing, our line runs 24/7 availability-based, and if the diagnosis lands in replacement territory, the decision math lives in our guide on whether an AC needs repair or replacement, with a free estimate pricing a new air conditioner installation beside the repair. A diagnostic visit typically runs $100 to $150 CAD in the GTA; the full repair cost bands by failure type are in the decision guide above rather than repeated here.

Staying safe while you wait for the repair

A Mississauga house without AC in a heat wave heats up fast, and the goal until the technician arrives is managing the household, not the equipment. Close blinds and curtains on the sun side, run fans to move air across people rather than trying to cool the room, spend the hottest hours on the lowest floor or basement where it can be several degrees cooler, drink water steadily, and skip the oven. During an Environment and Climate Change Canada heat warning, treat cooling as a health need: air-conditioned public spaces and the Region of Peel’s cooling spaces exist for exactly this, and anyone showing signs of heat illness, dizziness, confusion, or a rapid pulse, needs 911, not a repair truck. None of this fixes the AC, and all of it is what actually matters for the hours in between.

AC stopped working: frequently asked questions

Who do I call when my AC stops working in Mississauga?

Call a licensed HVAC company whose refrigeration work is done by certified 313A or 313D mechanics; Aire One Peel’s line at 905-564-8545 runs 24/7 with no after-hours charge. Two exceptions route elsewhere first: a burning smell or repeat breaker trips means the system goes off at the breaker before any call, and a whole-home power outage belongs to Alectra Utilities.

What should I check before calling for AC repair?

Five things, in order: the thermostat is on cool and set below room temperature, the breaker gets one reset only, the filter is not clogged, any ice on the lines gets a fan-only thaw for 2 to 3 hours, and the outdoor unit and condensate drain are clear. These take about ten minutes, cost nothing, and revive a real share of dead systems without a visit.

Is a broken air conditioner an emergency?

It becomes one in two cases: an electrical burning smell or a breaker that keeps tripping, which means off at the breaker immediately, and a heat warning with infants, seniors, or medically vulnerable people in a hot home, which is a health situation before a repair one. In that second case, cool spaces come first, the Region of Peel’s cooling spaces exist for it, and heat illness symptoms mean 911.

Why did my AC suddenly stop working?

The most common culprits are unglamorous: a tripped breaker, a dead thermostat battery, a clogged filter that iced the coil until the system shut itself down, or a full condensate pan tripping the float switch. Beyond those, failed capacitors and contactors are the classic sudden-death parts, which is exactly what the ten-minute checks separate from a real repair call.

What should I do if there is ice on my AC?

Switch cooling off, run the fan only for 2 to 3 hours to thaw the coil, and change the filter, since starved airflow is the most common cause of icing. If the system ices up again after a clean thaw and a fresh filter, stop there and book a visit, because recurring ice usually points to low refrigerant, which is certified-mechanic territory, never a top-up-and-hope fix.

How do I stay cool while waiting for AC repair during a heat wave?

Close blinds on the sun side, aim fans at people rather than the room, spend the hottest hours on the lowest floor, drink water steadily, and skip the oven. During an Environment and Climate Change Canada heat warning, use air-conditioned public spaces or the Region of Peel’s cooling spaces, found through peelregion.ca or 211, and treat dizziness, confusion, or a rapid pulse as a 911 call, not something to wait out.

Final verdict: emergency AC repair Mississauga homeowners can count on

When your AC stops working in Mississauga, the order is: breaker off for anything electrical, people into cool spaces during a heat warning, ten minutes of free checks, and then one call to a licensed company with certified 313A or 313D refrigeration mechanics, which is us at 905-564-8545, 24/7 with no after-hours charge and the diagnosis in writing. If that diagnosis opens the replacement question, the math is already waiting in our guide on whether your AC needs repair or replacement, with a free estimate to put real numbers on both paths.

Sources and references

O. Reg. 463/10, Ozone Depleting Substances and Other Halocarbons, Government of Ontario Skilled Trades Ontario, 313A and 313D refrigeration and air conditioning mechanic trades Electrical Safety Authority (ESA), licensed electrical work requirements Environment and Climate Change Canada, heat warnings Region of Peel, heat response and cooling spaces