In short
- Burners that light and go out after a few seconds point first to the flame sensor: $75–$200 on a Canada-wide guide, $100–$200 on one Ottawa firm's published list.
- A heat pump heats air to about 25–45°C and a furnace to 55–60°C, says Natural Resources Canada, so cooler air in a heat pump home can be normal.
- Under Ontario law, furnaces must be maintained by TSSA-registered contractors, who must hire TSSA-certified gas technicians.
Typical prices in Ottawa
| Job | Typical range | Notes |
|---|---|---|
| Diagnostic or service call | $80–$150 | Canada-wide guide; often credited toward the repair, confirm when booking |
| Flame sensor replacement | $75–$200 | Canada-wide guide |
| Flame sensor cleaning or replacement | $100–$200 | One Ottawa firm’s published list |
| Ignitor replacement | $150–$300 | Canada-wide guide |
| Pressure switch replacement | $150–$350 | One Ottawa firm’s published list |
| Draft inducer motor replacement | $300–$700 | One Ottawa firm’s published list |
| Gas valve replacement | $300–$700 | Canada-wide guide |
| Control board replacement | $400–$900 | Canada-wide guide |
| Electric furnace: limit switch / sequencer / heating element | $100–$250 / $150–$350 / $150–$400 | Canada-wide guide |
| After-hours surcharge | $100–$200 or more | Canada-wide guide; one Ottawa firm lists $50–$150 |
Sources. HomeStars, Furnace Repair Costs in Canada in 2026, seen 29.10.2026. One Ottawa firm’s published list: Furnace Repair Cost Ottawa: What to Expect Before You Call, published 25.03.2026, seen 29.10.2026. Ottawa range and labour: HomeStars, How Much Does HVAC Cost in Ottawa?, updated 21.08.2026, seen 29.10.2026. Causes: Carrier Canada, Why is my furnace blowing cold air, seen 29.10.2026. Heat pumps: Natural Resources Canada, Heating and cooling with a heat pump, modified 24.12.2025, seen 29.10.2026. Rules: TSSA, Be fuels wise, TSSA, Find a Registered Fuels Contractor, Ontario, guide for home renovation businesses, Ontario, rules for businesses entering contracts at a consumer’s home, Ontario, carbon monoxide safety, all seen 29.10.2026.
When the cold air starts
The timing narrows the search. Four patterns:
- The first minute of a cycle. Carrier’s Canadian page says some furnaces hold the blower back until the air heats. Cold air past a few minutes is a reason to call.
- Warm for a few minutes, then cold. The burners stopped while the blower kept running: an overheating safety switch, or a blocked drain on a high-efficiency unit.
- Cold from start to finish. The burners never lit or went out within seconds, or the system is set to cool or fan only.
- Warm near the furnace, cool at the far rooms. Carrier lists leaking ducts among the causes; heat is lost before it reaches the register.
Put the matching pattern in your request.
The thermostat side
Carrier’s list starts at the thermostat: cool mode by mistake, a lowered set point, or a schedule thrown off by the clock change. A fan left on On runs between heating cycles and pushes room-temperature air that feels cold. Write down the mode, the set temperature and the fan setting. A recently replaced thermostat deserves a line too: thermostat installation.
Burners that light, then go out
A flame sensor confirms the burner has lit. When it is coated, the furnace lights briefly and shuts down; the same Ottawa firm lists flame sensor work among its most common furnace repairs. An ignitor that has failed means the burners never light. A pressure switch problem typically shows up as a furnace that starts but does not fire, often with a flashing code.
High-efficiency furnaces add a condensate drain. The same Ottawa firm writes that the drain can clog or freeze in an Ottawa winter when it exits near ground level, and the furnace then shuts down. If your furnace vents through white plastic pipes, mention it. More on these units: high-efficiency furnaces.
Overheating and the high-limit switch
The limit switch measures air temperature inside the furnace. When airflow is choked, the heat exchanger overheats, the switch shuts the burners off and the blower carries on with unheated air. Carrier names a clogged filter and too many closed supply vents among the causes. A switch that keeps tripping points to an airflow problem, and the company should name it along with any part it replaces. Related: short cycling.
Heat pump, oil and electric homes
Heat pumps and hybrids. Natural Resources Canada says a heat pump heats air to about 25–45°C and a furnace to 55–60°C. During defrost the heat pump cools the air in the ductwork, and a hybrid runs only one of the two at a time. Cold air during the furnace’s turn is a fault; say which unit was running. See hybrid heating.
Oil and propane. Carrier lists a low or empty tank and a clogged oil filter.
Electric furnaces. The Canada-wide guide lists elements, sequencers and limit switches as common repairs.
What moves the price
HomeStars’ Ottawa guide spans $100–$7,000 for furnace repairs, with labour at $75–$150 an hour. A flame sensor or ignitor sits at the low end of the lists above; a gas valve, control board or inducer motor costs more. The Canada-wide guide adds that parts for furnaces past age 15 may need ordering and a second visit. After-hours calls add a surcharge. More figures: furnace repair cost guide.
What the quote should list
The quote should name the part, its cause, labour, the diagnostic fee and whether it is credited, any after-hours charge and HST. In Ontario, a home repair over $50 needs a written agreement, and a business cannot charge more than 10% above an estimate in it unless you sign a change.
Gas work in Ontario goes through a TSSA-registered contractor. TSSA’s online registry lets you look a company up by name and city; TSSA says the listing is no endorsement. During a repair visit, Ontario’s rules bar a company from signing you to a new furnace on the spot unless it already has a contract with you, asked in advance to offer one, and you agreed.
Who handles your request
Ottawa Heating Desk passes your request to one independent local heating company. That company calls you back, finds why the air is cold, prices the repair and does the work.
Questions to ask the company
- Which parts do you suspect from my description, and what does each cost?
- Is the diagnostic fee credited toward the repair if I go ahead?
- If a safety switch shut the burners off, what caused it?
- If the part must be ordered, is the second visit charged?
- Can I see the total with HST in writing before you start?
Have this ready for the call
- When the air turns cold: from the start, after a few minutes of warm air, or all the time
- What the thermostat shows: mode, set temperature, and whether the fan is on On or Auto
- Furnace make, model and age, from the label inside the furnace door
- Any blinking light or code on the furnace, written down or filmed
- Fuel: natural gas, propane, oil or electric, and whether a heat pump also heats the house
- When the filter was last changed, and whether the stove or water heater works on gas
Questions people ask
The vents blow cold for a minute after the furnace starts. Is that a fault?
Often it is the blower delay. Carrier’s Canadian page says some furnaces hold the blower back so the air heats first; cold air past a few minutes is a reason to call.
Can a clogged filter make the air cold?
Yes. The Canada-wide guide says a badly restricted filter can make a furnace overheat and shut down on its high-limit switch, which can look like a failed part.
We added a heat pump and the air feels cooler. Is it broken?
It can be normal. Natural Resources Canada says people switching from a furnace may notice the lower air temperature of a heat pump. Say in your request which unit was running when the air felt cold.
Should I approve the repair on the first visit?
For a flame sensor or ignitor, approving on the first visit is reasonable, says the Canada-wide guide. For anything over $300, such as a blower motor, control board or gas valve, it suggests a second opinion.
The CO alarm went off while the furnace was blowing cold air. What now?
Ontario says get everyone out of the home and call 9-1-1 from outside. Once the home is cleared, mention the alarm in your request.
