End of Cooling Season: Shutting Down the AC and Waking the Furnace

The Two Weeks When Neither System Is Doing Much

If you are researching End of Cooling Season: Shutting Down the AC and Waking the Furnace, you have probably noticed the air conditioning has not run for days while the furnace has not yet been asked for anything. September in the Lower Mainland is the gap between the seasons — warm afternoons, cool damp mornings, a house that mostly manages on its own.

The changeover is not complicated, but it is easy to do badly. Much of the trouble we see in November comes from well-meant autumn tidying rather than neglect: a condenser sealed under a fitted cover, a furnace fired for the first time on a cold Sunday night, a filter left in place since May.

What follows is the order our team at Northwind Heating, Cooling & Fireplace Showroom works through on a September afternoon. Most of it takes an hour. The one part you cannot do yourself is the combustion and safety check on the furnace.

Closing Out the Air Conditioning

Air conditioners here have no fixed shutdown date, and a warm stretch in late September is common. Wait until you have gone a fortnight without touching the cooling setpoint.

The outdoor disconnect: the argument both ways

Beside the outdoor unit sits a small weatherproof box holding a pull-out disconnect or breaker. Whether to switch it off for winter is a genuine difference of opinion among technicians, not a settled rule.

• For switching it off. It removes any chance of the unit starting on a cold day, when a compressor can be damaged moving oil that has thickened.

• For leaving it on. Many air conditioners have a crankcase heater that keeps refrigerant out of the compressor oil, and it needs power at the unit to work.

• The middle ground. A thermostat set to heating never sends a cooling call, which is protection enough in a climate as mild as ours.

If you are unsure which you have, leave it alone. Anyone who says it must be switched off is stating a preference.

Clearing the leaves and debris

Switch the power off at the disconnect first. Clear leaf litter out of the base pan by hand — debris left sitting there holds moisture against the metal all winter and is the usual reason a base pan rusts through early. Cut shrubs and ornamental grasses back to roughly half a metre of clear air on every side. If the coil fins are matted, a gentle rinse with a garden hose from the inside out is fine; a pressure washer flattens the fins and permanently reduces airflow.

Covers: The Mistake We See Every Autumn

Every September, homeowners buy a fitted vinyl cover that zips over the whole condenser. It is the one job on this list that is worse than doing nothing.

Why a full wrap works against the equipment

An outdoor unit is built to sit outside, and rain and snow do it no harm. Trapped moisture does. Condensation forms under the vinyl, cannot evaporate, and sits against the coil and the electrical compartment for months. A sealed cover also creates what a rodent wants in November — a dry, enclosed space with insulated wiring inside to chew.

A breathable top cover is the better idea

If you want to cover anything, cover only the top. A weighted piece of plywood, or a top-only cover that leaves all four sides open, keeps leaves and cedar needles out of the fan while air still moves through the cabinet. That is the entire honest benefit a cover offers.

Heat pumps must not be covered at all

A heat pump is not an air conditioner resting for the winter — it is your heating system, and it runs through January. Covering it, even over the top, blocks the airflow it needs and interferes with the defrost cycle that clears frost from the outdoor coil.

They want clear space instead: nothing stacked against the cabinet, and a path for meltwater to drain away from the base rather than freeze underneath. Keep snow cleared below the level of the coil. The same applies to the outdoor unit of a ductless system.

Waking the Furnace

The furnace has sat unused since roughly March. Nothing has gone wrong in that time, but the point of a September start-up is to find what has quietly changed while the weather still forgives a delay.

The filter that has sat all summer

Change it before anything else. With central air, that filter has worked the entire cooling season, because the same blower and ductwork serve both systems. With a furnace only, it has still been collecting whatever came through open windows since spring.

Point the airflow arrow toward the furnace. Most households do well changing a standard filter every two to three months, more often with pets or nearby construction. If you are weighing a higher-rated filter, our guide to choosing the right filter for a Lower Mainland home covers the trade-off between filtration and the static pressure an older blower can tolerate.

The burning smell on the first firing

A faint scorched-dust smell for the first ten to twenty minutes is almost always summer dust burning off the heat exchanger, not a fault. Open a couple of windows and let it run; it clears within a cycle or two.

What is not normal: a sharp chemical smell, burning that persists past the first hour, visible smoke, or any smell of gas. Those mean shutting the system down, and a gas smell means leaving the house and calling the gas utility from outside.

Test on a mild day, not the first cold night

Pick a mild afternoon, set the thermostat several degrees above room temperature, and let the furnace run two or three complete cycles. You are watching for clean ignition, steady warm air at the registers, no grinding from the blower, and a normal shutdown rather than a short cycle.

This is why so many furnaces fail on the first genuinely cold night — the fault was already sitting in an igniter or a pressure switch in September, and the first hard run found it. Found now, it is an appointment next week.

The Thermostat, Before You Need It

Changeover to heating

Switch the thermostat from cool to heat and confirm it actually calls for heating, rather than sitting in an auto mode that hunts between the two on a warm afternoon. If it is programmable, review the schedule — the one you set in June for a hot, empty house is the wrong shape for a dark October morning.

Batteries

Replace them now if your thermostat takes them, even if the display looks fine. Dying batteries can drop the heating call intermittently or lose the programme, and that fault is hard to diagnose because everything downstream tests perfectly.

Clearances, Inside and Out

The area around the furnace

Furnace rooms accumulate things over a summer. Move paint, solvents, aerosols and cleaning products well away from the appliance — a gas furnace draws air from the space around it. Clear the off-season storage that has drifted in, check that any louvred door or combustion air opening is not blocked by shelving, and confirm the switch on the wall beside the furnace, which looks like a light switch, has not been flipped off by someone tidying.

The outdoor intake and exhaust vents

High-efficiency furnaces vent through a pair of plastic pipes out a side wall rather than up a chimney, often a metre or so above grade. One draws combustion air in, the other pushes exhaust out, and both must stay clear. Cedar debris, spider webs, a wasp nest, a shrub grown across the openings, or a stacked bin will all restrict them. A blocked vent usually shuts the furnace down on a safety switch, at the least convenient hour.

Frequently Asked Questions

Should I turn off the disconnect to my air conditioner for the winter?

It is optional, and leaving it on is the safer default unless you know your system has no crankcase heater. That heater keeps refrigerant from settling into the compressor oil in cold weather, and it only works with power at the unit. Setting the thermostat to heating already prevents an accidental cooling call. If you do switch the disconnect off, restore power several hours before running the system next spring.

Should I cover my air conditioner in the winter?

Do not wrap an air conditioner in a fitted cover — it traps moisture against the coil and electrical components and gives rodents a sheltered place to nest and chew wiring. Outdoor units are built to sit in rain and snow. The only cover worth using is a breathable top-only one that leaves all four sides open.

Can I cover my heat pump for the winter?

No — a heat pump runs all winter as your heating system and must never be covered, even on top. Blocking airflow interferes with the defrost cycle that clears frost from the outdoor coil, which can ice the unit up in exactly the weather you need it. Keep the area around it clear and let meltwater drain away from the base.

Why does my furnace smell like burning when I first turn it on?

A faint burnt-dust smell for the first ten to twenty minutes of the season is normal and comes from summer dust burning off the heat exchanger. Open a window and let it run; it usually clears within a cycle or two. Smoke, a sharp chemical smell, or burning that lasts more than an hour needs inspection. Any smell of gas means leaving the house and calling the gas utility.

When should I test my furnace before winter?

Test it on a mild day in September rather than on the first cold night. Set the thermostat several degrees above room temperature and let the furnace complete two or three full cycles while you check for clean ignition, steady warm air and a normal shutdown. A fault found now becomes an appointment next week; the same fault in November becomes an after-hours wait.

How often should I change my furnace filter?

Most homes need a standard one-inch filter changed every two to three months, and always at the seasonal changeover after it has run through the cooling season. Pets, a gravel driveway or nearby construction shorten that interval noticeably. Thicker pleated media filters in a dedicated cabinet often last a season or more.

Book the Service Now, Not in November

Everything above is homeowner work. What it does not cover is the part that needs instruments: burner and flame inspection, heat exchanger condition, gas pressure, combustion analysis, safety controls, and the condensate drain that has sat dry since March. September or early October is the sensible time for it. From the first genuinely cold week onward, every contractor in Surrey, Langley and Delta works through no-heat calls first.

If you would rather not track the timing yourself, a service agreement schedules the visit and keeps a record of what the equipment has done year to year — useful on the systems we see in homes built between the 1960s and 1990s. Book now and you choose the day. Book in November and the calendar chooses for you.

Northwind Heating, Cooling & Fireplace Showroom has been installing and servicing heating systems, cooling, heat pumps, ductless systems, fireplaces, water heaters, outdoor heating and indoor air quality equipment across Surrey, Langley, Delta, White Rock and the wider Lower Mainland since 1989, and is a registered CleanBC contractor. If you would like the seasonal service booked before the weather turns, Get in touch.