Air Conditioner Questions, Answered

A central air conditioner in Canada lasts 12 to 15 years, and a well-maintained unit reaches 18–20.

Yes, if your Toronto home has no ducts or has a room the ducts cannot reach: century homes on radiators, third-floor bedrooms in semis, basement apartments, additions and condos.

An air conditioner that cools but leaves the house clammy is usually oversized: it drops the temperature in 8–10 minutes and shuts off before it has pulled much water from the air.

Replace both if both are over 12 years old: bundling saves $1,000–$2,500 because labour, sheet metal and electrical overlap, and combined installs land at $9,500–$15,000 in the GTA.

A central AC replacement on existing ductwork takes 4 to 8 hours — one day for a two-person crew, with cooling running before they leave.

Most AC repairs in the GTA cost $150–$800.

When an AC will not turn on, the cause is usually electrical and usually cheap: a thermostat not calling for cooling, a tripped breaker or blown fuse in the outdoor disconnect, a failed capacitor or contactor, or a safety switch on the condensate drain.

An AC leaks water inside the house when condensate from the evaporator coil cannot reach the drain.

An air conditioner gets loud for a reason you can usually name by the sound.

A musty smell when the AC turns on comes from mould or bacteria growing on the wet evaporator coil, in the condensate pan, or on a damp filter, and the blower pushes it through the ducts in the first minute of each cycle.

An AC refrigerant recharge in the GTA costs $300–$800+ when done properly, because the price includes finding and repairing the leak, not just adding gas.

Replacing an AC capacitor costs $150–$350 in the GTA, including the part, the labour and the trip.

An AC compressor is the most expensive part in a central air conditioner, and replacing it sits well above the $150–$800 band that covers most AC repairs; the total is often close to the cost of a new unit at $3,500–$7,500 installed.

A ductless mini-split in Ontario costs $4,000–$7,000 installed for a single-zone system, $7,500–$11,000 for two zones and $10,000–$16,000+ for three or four.

A central air conditioner should be serviced once a year, in spring before the first hot week.

Yes.

Most central air conditioners should not run when the outdoor temperature is below about 15°C.

An AC trips the breaker when it pulls more current than the circuit allows.

A correctly sized single-stage air conditioner runs 15 to 20 minutes per cycle on a warm day, two or three times an hour.

Your second floor is hot in summer because warm air rises and collects under a roof baking at 50°C or more, while a single air conditioner run by a main-floor thermostat shuts off before the bedrooms cool.

For a like-for-like central AC replacement, many Ontario municipalities issue no building permit, but rules vary by town, so confirm with your building department.

Usually yes, if the repair is small.

A standalone air conditioner tune-up in the Burlington, Oakville and Hamilton area costs $120–$250 and takes 45 to 90 minutes.

The best time to buy an air conditioner is in the shoulder seasons — mid-September to October, or March to mid-May — when installers have open calendars, you can compare two or three quotes calmly, and you are not deciding in a heat wave.

A burning smell from an air conditioner is always a fault, because nothing in cooling mode is supposed to get hot enough to scorch.

Yes.

The signs of an AC refrigerant leak are ice on the large copper line or the indoor coil, a hissing sound, air from the vents that is only slightly cool, run times that stretch for hours, and oily residue on fittings or service valves.

An AC makes a hissing sound for one of three reasons.

An outdoor AC fan that is not spinning usually has a failed run capacitor, seized fan-motor bearings, a burnt contactor, or no power from a tripped breaker or pulled disconnect.

An AC compressor that won't turn on while the outdoor fan runs has usually lost its start: a failed run capacitor, an open contactor pole, a tripped internal overload or an open pressure switch.

When the outside AC unit is not running but the inside fan is, the outdoor unit has lost either its 240 V power or its 24 V signal.

An AC that keeps turning on and off in runs shorter than about 10 minutes is short cycling.

To reset an air conditioner, set the thermostat to Off, switch the AC breaker off for 5 minutes, turn it back on, then set the thermostat to Cool.

An outdoor AC unit buzzing is most often a pitted or chattering contactor, or a failed dual run capacitor leaving the compressor or fan motor humming without starting.

A single click when the air conditioner starts and another when it stops is the contactor or a relay doing its job.

An AC that won't turn off is doing one of two things.

A frozen AC takes 1 to 3 hours to thaw with cooling switched off and the fan set to ON, and up to 24 hours when the indoor coil is encased in a solid block of ice.

An AC smells like vinegar when bacteria growing on the wet evaporator coil, in the condensate pan or in the drain trap give off sour, acetic odours.

An AC that is not working after a power outage usually has a tripped breaker, a thermostat that rebooted with lost settings, or a 5-minute compressor lockout still counting down.

An AC that won't start after winter usually has its power still off: the outdoor disconnect pulled or the breaker switched off in the fall, or the thermostat left in Heat.

Yes, you can hose off your AC condenser, and once a year you should.

To unclog an AC drain line, switch the cooling off, then put a wet/dry vacuum on the drain outlet or on the cleanout tee beside the furnace coil and run it for a minute or two to pull the blockage out.

A bad AC capacitor shows up as an outdoor unit that hums without starting, a fan that needs a push, slow or hard starts, clicking, or warm air on hot afternoons only.

An AC that bangs when it starts up usually has a compressor that is hard-starting on a weak capacitor or worn windings, or one that has broken its mounting grommets or an internal spring.

An AC that gurgles or bubbles is moving either refrigerant or water.

You can run your AC without a filter for the few hours it takes to buy a new one, but not for days.

A condensate pump overflows when water arrives faster than it leaves: the float is stuck, slime has jammed the reservoir, the motor has failed, or the vinyl discharge tube or check valve is blocked or kinked.

Lights that dip for a fraction of a second when the AC starts are normal: a compressor draws several times its running current for an instant at start-up.

Yes.

Most single rooms need a 9,000 or 12,000 BTU mini-split: about 9,000 BTU for up to 400 square feet, 12,000 for 400 to 550, 18,000 for 550 to 850 and 24,000 for open areas up to about 1,200.

No.

Mostly no.

A single-zone mini-split installed back to back, with the outdoor unit directly behind the indoor head, takes about four to six hours, one working day at most.

Error E73 on a Nest thermostat means the thermostat detects no power on the Rc wire, the 24-volt feed from your cooling system.