Before a Furnace Service Call: Notes to Prepare and Questions to Ask

A furnace that stops heating can leave you unsure what to do next. Preparing a clear description helps when you book a service visit. This guide explains which observations to record without opening the furnace, the emergency situations where you should leave immediately, and the questions to ask when a technician arrives.

You do not need to find the failed part before asking for help. If you need local service, our Markham HVAC services page covers the work Furnace King handles in the area.

Start With Your Safety

Before any troubleshooting, rule out the situations where you should not touch the furnace at all.

• If you smell natural gas (a rotten-egg odour), leave the home right away, leave doors open if you can do so safely, and call Enbridge Gas’s 24-hour emergency line at 1-866-763-5427 or dial 911 once you are outside. Do not use switches, lighters or phones inside the home. Enbridge’s steps are listed on its smell gas safety page.
• If a carbon monoxide alarm sounds, get everyone out into fresh air and call 911 or your fire department from outside. Health Canada’s advice is not to search for the source yourself and not to go back in until a qualified professional says it is safe. See Health Canada’s carbon monoxide guidance.
• If you see smoke or signs of fire, leave the home and call 911 from outside. If there is a burning smell without smoke or fire, stop using the furnace and call for service rather than running it again.

Note the Settings and Symptoms Without Opening the Furnace

You do not need to diagnose the fault before calling. If there is no gas smell, carbon monoxide alarm, smoke or burning smell, note the thermostat setting and the displayed room temperature. Describe what happens when the thermostat calls for heat: nothing, a click, a hum, or a start followed by a shutdown.

Write down any error code visible through the furnace’s viewing window without removing a panel. If the model label is visible on the outside, photograph it. If it is behind a panel or you cannot reach it safely, leave that information for the technician. Do not open the cabinet, test gas components, bypass a safety switch or repeatedly reset the equipment.

Describe the Pattern Rather Than Guessing the Cause

Tell the technician whether the furnace never starts, runs without warming the home, or stops before reaching the thermostat setting. Mention new noises, rooms that feel colder than usual, and whether the problem is constant or comes and goes. These observations help describe the problem; they do not establish which part has failed.

What a Furnace Repair Visit Usually Involves

Knowing the process makes the visit smoother. While every furnace and every problem is different, a repair visit generally follows this order.

1. A conversation about symptoms. The technician asks when the problem started, what you have noticed and what you have already checked. The notes you took about codes, noises and timing help here.
2. Inspection of the system. The technician looks at the thermostat, filter, ignition, burners, blower, venting and safety controls to find the cause instead of guessing.
3. A clear explanation of the fix. You should hear what failed, what repair is recommended and what it involves before work begins. Anything beyond a routine visit depends on what the technician finds, so ask for the details before approving work.
4. The repair and a test. After the repair, the system is run through a heating cycle to confirm it operates correctly.

Furnace King’s heating services page describes the furnace repair and installation work we handle.

Questions to Ask During the Visit

Ask what the technician found, what work is recommended, what it will cost and what is included before approving the repair. Ask which symptoms should prompt another call and whether any follow-up is needed.

If replacement is raised, ask how the furnace’s condition and the proposed repair affect that recommendation. Our separate furnace repair versus replacement guide covers that decision in more detail.

How to Describe the Problem Clearly

A clear description speeds up diagnosis, whether you phone us or fill in a form. Before you call, jot down the following so you can answer quickly.

• When the problem started, and whether it happens all the time or only at certain times of day.
• What the furnace does when the thermostat calls for heat: nothing at all, a click, a hum, or a start followed by a shutdown.
• Any noises, smells or lights on the control board, described as precisely as you can without opening the furnace.
• The brand and model number from the label on the furnace, and roughly how old the system is.
• Any recent servicing, filter changes or thermostat adjustments you already made.

Photos of the model label and any visible error light are also useful. Only collect details that are safely visible without tools or opening the unit. Leave anything else for the technician.

Keep Maintenance Separate From the Immediate Problem

When booking, explain the current symptoms first. If you also want routine servicing, ask whether it can be discussed during the visit. Our HVAC maintenance page covers that separate service.

Frequently Asked Questions

Should I keep troubleshooting if I smell gas?

No. Leave the home immediately without using switches, flames or phones inside. Once outside, call Enbridge Gas at 1-866-763-5427 or 911. Follow Enbridge Gas’s emergency guidance.

What should I do if a carbon monoxide alarm sounds?

Get everyone outside into fresh air and call 911 or your fire department. Do not search for the source or go back inside until a qualified professional says it is safe. See Health Canada’s carbon monoxide guidance.

What information should I have ready for a service call?

Note when the problem started, what happens when the thermostat calls for heat, and any visible error code. Record the brand and model only if you can read the label without opening the unit. Tell the technician about any recent maintenance or changes in how the system runs.

Book a Visit With Your Notes Ready

If your furnace is not heating, is making new noises or keeps shutting off, call Furnace King at (905) 564-5464 or contact us online to describe the problem. Have the furnace brand and model number, the symptoms and any codes you noted ready, and we will help you decide the next step. If the issue is urgent, our emergency services page explains how to reach us. For everything we do for Markham homes, see our Markham HVAC services page.