These signs mean the system is overdue for service
A furnace that lights, runs for a minute and shuts off is short cycling. The usual causes are a dirty flame sensor that can no longer prove the flame, a clogged filter that lets the heat exchanger overheat until the high-limit switch opens, or a pressure switch that trips because the inducer cannot pull a draft through a blocked vent or a full condensate trap. A gurgling sound from the cabinet, water on the floor beside the furnace or an error code on the control board points the same way.
On the cooling side, warm air from the registers, frost on the larger copper line at the outdoor unit, water dripping from the indoor coil or a breaker that trips when the compressor starts all suggest low refrigerant charge, a dirty coil or a weak start capacitor. These are worth booking before the system stops altogether; see air conditioner repair if it already has.
If a carbon monoxide alarm sounds, leave the house and call the gas utility's emergency line from outside. The Ontario Fire Code requires a working CO alarm next to each sleeping area in a home with a fuel-burning appliance, a fireplace or an attached garage, and a tune-up is a good time to confirm yours are in place.
Condensing furnaces in the west end fail at the vent and the drain
Homes in the Winston Road Neighbourhood, around the Casablanca Road interchange and in the GO Station Secondary Plan Area mostly have high-efficiency condensing furnaces. These extract so much heat from the exhaust that water condenses inside the unit. That water runs through a condensate trap and drain line, and the cooled exhaust leaves through plastic pipes in the side wall.
Both are common failure points. A trap full of sediment or a drain line frozen where it runs near an exterior wall backs water up into the collector box, and the pressure switch shuts the furnace down. Snow drifted over the side-wall terminations, or frost built up on the exhaust during a cold spell, does the same thing from the outside. Maintenance clears and flushes the trap, checks the drain slope and confirms the intake and exhaust pipes have proper clearance above grade and from each other.
These tighter houses also rely on a heat-recovery ventilator for fresh air. Its filters and core are easy to forget, and a clogged core leaves the house stuffy and humid. The tune-up includes the HRV filters and a look at the core.
Older chimneys and post-war ducts need a different check
In Grimsby Beach cottages and the older houses along Main Street East and West, gas equipment often vents into a chimney that was built for wood or coal and relined later, or not at all. In the Lakemount Terrace Subdivision, many original oil or coal furnaces were replaced with high-efficiency units, leaving a gas water heater venting alone into a chimney far too large for it. A small, cool flue gas stream in a big masonry chimney may not draft, and combustion products can spill back into the basement.
For these homes the technician runs a spill test at the draft hood of the water heater and any other naturally vented appliance, looks at the liner where it is visible and checks the return-air path. Post-war ductwork often has too little return, which makes a modern blower work against high static pressure and shortens its life.
A furnace tune-up measures pressure, combustion and airflow
Under O. Reg. 212/01, gas appliances in Ontario must be serviced by a registered contractor to the CSA B149.1 installation code, and work is performed by TSSA-certified gas technicians. The visit covers the following measurements and checks.
Inlet and manifold gas pressure are read with a manometer and set to the rating plate. A combustion analyzer reads carbon monoxide and oxygen in the flue gas, which shows whether the burners are getting the right mix of gas and air. Temperature rise across the heat exchanger is compared with the range printed on the furnace; too high a rise means restricted airflow. External static pressure across the blower shows whether the filter and ducts are choking it. The flame sensor is cleaned and its signal read in microamps, the igniter is inspected, and the heat exchanger is examined for cracks or rust-through. Safety switches, including the high limit and pressure switch, are tested to confirm they open when they should.
An air conditioner tune-up measures charge, not just temperature
Work is performed by 313A refrigeration and air conditioning mechanics, the compulsory trade in Ontario for anyone who handles refrigerant. The technician measures superheat and subcooling with gauges and temperature clamps, which together show whether the refrigerant charge is correct for the metering device. Topping up without those readings can overcharge the system and damage the compressor.
The outdoor coil is cleaned, the start and run capacitor is tested against its rated microfarads, the contactor is checked for pitting and the compressor and fan motor amp draw are recorded. Indoors, the evaporator coil and condensate drain are cleared so water goes to the floor drain rather than the ceiling below. The same measurements apply to heat pumps, which also run through the winter.
Timing, manufacturer warranties and the written price
Book cooling service in spring and heating service in early fall, before the first long run of the season. The lake moderates Grimsby's weather, keeping summers cooler and winters milder than inland, but the equipment still has to carry the hottest and coldest weeks without a fault.
Many manufacturers' warranty terms ask for annual maintenance by a qualified technician, so keep the dated service record. If a measurement shows a worn part, you see a written price and decide before anything is fitted. For an older unit, our guide on whether a 25-year-old furnace should be repaired or replaced explains the trade-off, or request a quote to book a visit.