# Furnace Not Working? 9 Things to Check Before You Call

> If your furnace stops working, first check the thermostat (mode, setpoint, batteries), the furnace filter, the furnace power switch and breaker, the blower door, and the outdoor intake and exhaust pipes for snow or ice. If those are fine, or you smell gas, hear banging or your carbon monoxide alarm sounds, stop and call a licensed technician.

Source: https://lancasterheatingandcooling.ca/furnace-not-working-checklist/

A furnace that stops working on a cold Hamilton night is stressful. Before you book a service call, a few simple
checks can sometimes get the heat back on, and they'll help our technician diagnose the problem faster if you do
need us.

> **Safety first:** if you smell gas (a rotten-egg smell), hear your carbon monoxide alarm, or see scorch marks or
> smoke, don't troubleshoot. Leave the house and call 911 from outside.

## 1. Check the thermostat

- Make sure it's set to **Heat**, not Cool or Off.
- Set the temperature a few degrees above the current room temperature.
- Check that the fan is set to **Auto**. "On" runs the fan constantly, even when the burners are off, so you'll
  feel cool air between cycles.
- Replace the batteries if the screen is blank or dim.
- For smart thermostats, check for a schedule, an "eco" or "away" mode, or a lost Wi-Fi connection.

## 2. Check the furnace filter

A clogged filter starves the furnace of air. It can overheat and shut the burners off as a safety measure, so you
get cold air or short cycling. Hold the filter up to a light: if you can't see through it, replace it.

## 3. Check the power switch and breaker

Most furnaces have a service switch that looks like a light switch, on or near the furnace. Make sure it's **on**.
Then check your electrical panel for a tripped furnace breaker. If the breaker trips again, leave it off and call
us.

## 4. Make sure the blower door is closed

Furnaces have a safety switch that stops the furnace from running when the front panel isn't seated properly.
After changing a filter, make sure the panel is fully closed.

## 5. Clear the outdoor vent pipes

High-efficiency furnaces vent through white plastic (PVC) pipes on an outside wall. Snow drifts, ice or a bird's
nest can block them, and the furnace will shut down. Carefully clear snow and ice away from both pipes.

## 6. Check the condensate drain

High-efficiency furnaces produce water that drains through a small hose or into a condensate pump. A clogged drain,
a frozen line or a full pump can shut the furnace off. Look for water around the furnace or a pump that's full.

## 7. Make sure the gas is on

Check that the gas valve to the furnace is open (the handle runs parallel to the pipe). If other gas appliances
such as the stove or water heater also aren't working, contact your gas utility.

## 8. Open the supply vents and return grilles

Closed or blocked vents make some rooms cold and can make the furnace overheat. Keep at least most vents open and
don't block return grilles with furniture.

## 9. Note any error codes or noises

Many furnaces have a small light that blinks a code through a window in the panel. Write it down, along with any
noises (banging, squealing, rumbling) and when they happen. It helps our technician arrive with the right parts.

## When to call a professional

Call a licensed technician if:

- The checks above don't fix it, or the problem keeps coming back.
- The furnace turns on and off rapidly (short cycling).
- You hear banging, grinding or squealing.
- The burner flame is yellow or flickering instead of steady blue.
- Your furnace is over 15 years old and needing more frequent repairs. It may be time to look at
  [furnace replacement](https://lancasterheatingandcooling.ca/heating/furnace-replacement/).

Lancaster Heating and Cooling offers [24/7 emergency furnace repair](https://lancasterheatingandcooling.ca/emergency/) across
Hamilton, Halton and Niagara. Call **[905-388-3333](tel:+19053883333)**.

Regular [furnace maintenance](https://lancasterheatingandcooling.ca/heating/furnace-service/) prevents many of these problems before they start.

## Furnace troubleshooting questions

### Why is my furnace blowing cold air?

Common causes are a thermostat set to "fan on" instead of "auto", a clogged filter causing the furnace to overheat and shut the burners off, a blocked condensate drain, or an ignition or flame-sensor fault. If checking the thermostat and filter doesn't fix it, call for [furnace repair](https://lancasterheatingandcooling.ca/heating/furnace-repair/).

### Is it safe to keep resetting my furnace?

No. If a furnace locks out more than once, it's protecting itself from a problem such as overheating, poor venting or a failed sensor. Repeated resets can make things worse; call a licensed technician instead.

### What should I do if I smell gas?

Don't touch light switches or appliances. Leave the house right away, then call 911 or your gas utility from outside.

### How much does furnace repair cost?

It depends on the cause and the part needed. Our technician will diagnose the problem and explain the cost before any work starts. Call [905-388-3333](tel:+19053883333).

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**Lancaster Heating and Cooling** — HVAC contractor serving Hamilton, Niagara and surrounding areas since 1955.
Phone (24/7 emergency): 905-388-3333 · Email: info@lancasterhvac.ca
Address: 1250 Stone Church Rd. E, Hamilton, ON L8W 2C8, Canada · Hours: Monday – Friday: 8:00AM – 4:30PM
Request a quote: https://lancasterheatingandcooling.ca/quote/