Furnace Not Heating? A Five-Minute Checklist

Before booking a repair, run through these checks. They solve a surprising number of no-heat calls and help you describe the problem if they don't.

Request an HVAC technician

1. Thermostat

Set it to heat and a few degrees above room temperature. Replace the batteries if the screen is blank. On smart thermostats, check that no schedule or eco mode is overriding your setting.

2. Power switch and breaker

Find the furnace power switch, often on a wall near the furnace or at the top of the basement stairs, and make sure it's on. Check the breaker panel for a tripped furnace breaker.

Diagram: the furnace power switch usually looks like a light switch, often with a red plate. It is easy to switch off by mistake.

3. Filter

A badly clogged filter can make the furnace overheat and shut itself down. Slide it out and look: if you can't see light through it, replace it with the same size.

Diagram: buy the size printed on the filter edge, and install it with the airflow arrow pointing toward the furnace.

4. Vents and returns

Make sure supply vents are open and return grilles aren't blocked by furniture or rugs. Closing too many vents can starve the system of air.

5. Error lights

Many furnaces have a small window with a blinking light. Count the blinks and match them to the code chart inside the panel door; note the code for the technician.

When to get help

If the checks don't help, the furnace starts and stops repeatedly, or you smell gas or burning, get a technician. See furnace repair.

Note what you find

Write down what you checked and anything unusual, such as sounds, smells or the error code, so the technician can start in the right place.

More HVAC guides

Heating or cooling trouble in Greater Victoria?

Send a request and an HVAC technician will get in touch. Requests answered 7 days a week.

Prefer email? [email protected]

Request an HVAC technician