A breaker that keeps tripping means the unit stays off
If the breaker for the outdoor unit trips, reset it once. If it trips again, leave it off. Repeated tripping usually points to a weak capacitor, a shorted fan motor, a wiring fault at the outdoor disconnect or a compressor that is starting to fail. Running it again and again can finish a compressor that might still have been saved.
The same goes for a burning smell at the vents, an outdoor unit that hums but whose fan does not turn, or a loud clank at start-up. Switch the system off at the thermostat and ask for a repair visit. These are electrical or mechanical faults, and they get worse with use.
Running but not cooling is usually airflow, a capacitor or a leak
Start with the simple checks. The thermostat is set to cool and below room temperature. The furnace filter is not clogged. The furnace door is shut tight, because the blower will not run with it open. Outside, the fan on top of the unit is turning and the coil fins are not packed with grass clippings or seed fluff.
If the fan outside is still and the unit hums, a failed capacitor or contactor is the usual cause. If both fans run but the air is barely cool, look at the copper line at the outdoor unit. Ice on that line, or on the coil above the furnace, means either too little air across the coil or too little refrigerant. Turn the cooling off and set the fan to on so the ice can melt before anyone tests it.
Low refrigerant always means a leak. A system does not use refrigerant up. Topping it up without finding the leak only puts off the next breakdown. Our guide on air conditioners running but not cooling goes through these checks in more detail.
Water by the furnace usually comes from the condensate drain
The cooling coil sits on top of the furnace and pulls water out of the air all day. That water runs to a drain through a small line, often with a trap or a pump. When the line clogs with sludge or the pump fails, the water ends up on the basement floor.
In Avalon and the other newer Caledonia homes, the high-efficiency furnace makes its own condensate and usually shares the drain line or pump with the air conditioner. A blocked line there can flood the floor in summer and shut the furnace down in winter. Check that the pump is plugged in and that its reservoir is not full, then call if the water keeps coming.
In the 1960s houses around Shetland Street, north of the river, central air was usually added later to the original ducts, which are often on the small side for cooling. Too little air over the coil makes it freeze, then drip heavily when it thaws. The fix there may be airflow, not the drain. In the older homes around Edinburgh Square with ductless wall units, a leaking indoor head usually means a blocked drain line or a unit that was hung without enough slope.
Refrigerant work is a compulsory trade in Ontario
Anything that opens the refrigerant circuit, such as finding a leak, replacing a coil or changing a compressor, has to be done by the right trade. Work is performed by 313A refrigeration and air conditioning mechanics.
A proper leak repair means finding the leak with a detector or soap test, fixing it, pressure-testing the system, pulling a vacuum to remove air and moisture, and then charging the refrigerant by weight to the manufacturer's figure. Skipping the vacuum or guessing at the charge leaves the system running poorly and shortens the compressor's life.
How a repair visit goes and when replacement makes more sense
The technician confirms the symptom with you, checks the filter, the drain and the electrical parts, then measures the temperatures and pressures across the system. You are shown what failed and why. You get the price in writing and approve it before any part is fitted.
If the unit is old, uses a refrigerant that is no longer made, or has a failed compressor, the repair can cost a large share of a new system. In that case you get both options, repair and replace, and you decide. Replacement can mean a new central air unit, or a heat pump that cools in summer and also takes some of the heating load off the furnace. Smaller faults like a capacitor, a contactor or a cleared drain are simply repaired.
Many of the faults on this page start with a dirty coil, a blocked drain line or a neglected filter. A spring check under furnace and AC maintenance catches most of them before the first hot week.