Furnace Not Working? Top 10 DIY Checks Before You Call

It’s cold. The furnace just quit. The house feels like a refrigerator. We know the panic—a furnace that’s suddenly silent can stop your whole day. And sometimes it’s the small stuff: a thermostat setting, a tripped breaker, or a clogged filter. Sometimes, it’s bigger. Briggs Heating is here to help you sort it out, step by step.

Whether you’re a homeowner or managing a business space, you want heat restored fast—without risking your safety or making things worse. Here’s how to check what you can, safely, before you call for emergency HVAC service.

Why Furnaces Fail: The Most Common Culprits

Furnaces have a few classic troublemakers. Sometimes it’s as simple as a thermostat set to “cool” instead of “heat.” Other times, a dirty air filter chokes off airflow. Power loss? Could be a tripped breaker or blown fuse. Gas models may lose their pilot light, or a safety switch may trip.

Think of your furnace like a relay race: if one runner (part) stumbles, the whole team stops cold. Knowing where to look can save you time, money, and a few shivers.

Quick Safety Checklist Before You Start 🛑

Your safety comes first—always. Before touching anything, take these quick precautions:

• Smell gas? Stop. Leave the area and call your gas provider or the fire department.
• Turn off power at the breaker before removing furnace panels.
• Check for carbon monoxide detectors. Make sure they're working and batteries are fresh.
• Have a flashlight ready in case you’re checking a dark utility room.
• Read your manual. Manufacturer instructions are your best friend (and always trump internet advice).
• Don’t force parts or bypass safety switches. That’s a shortcut to disaster.

The National Fire Protection Association (NFPA) and U.S. Consumer Product Safety Commission both warn: If you’re ever in doubt, err on the side of caution.

Step-by-Step: 10 DIY Checks to Try First

Let’s get hands-on. Here’s what to check before you pick up the phone:

1. Thermostat Settings

Is it set to “heat”? Is the temperature above the current room temp? Sometimes, the problem is as simple as a bumped switch or dead batteries. Replace batteries if needed.

2. Circuit Breaker or Fuse Box

Power out? Head to your home’s panel. Look for any tripped breakers (often labeled “furnace” or “HVAC”). Flip the switch off, then back on. For older homes, check for blown fuses.

3. Air Filter

A filter clogged with dust and pet hair can choke your furnace. Slide out the filter and hold it up to the light. If you can’t see through it, it’s time to replace. Filters should be checked monthly—especially during heavy use.

4. Gas Valve (for Gas Furnaces)

Check that the gas valve is fully open—parallel to the pipe is “open.” If you had recent service, a tech may have closed it and forgotten to reopen.

5. Pilot Light or Igniter

Older furnaces have a pilot light. If it’s out, refer to your manual for relighting instructions. Newer units use electronic igniters, which you can’t DIY repair but can visually inspect for obvious damage or dirt.

6. Furnace Switch

Look for a nearby wall switch—sometimes labeled “furnace” or “emergency shutoff.” It may look like a light switch. Make sure it’s on.

7. Vents and Registers

Walk through your space. Are all supply and return vents open and unblocked? Furniture, rugs, or boxes can unintentionally cover vents and limit airflow.

8. Furnace Door or Panel

Many furnaces have a safety switch that trips if the access panel isn’t securely closed. Make sure the panel is snug.

9. Thermostat Wiring

Loose or corroded wires can cause connection failures. Only check this if you’re comfortable and have turned off power to the unit. Look for obvious loose wires or corrosion.

10. Reset the System

Many furnaces have a small reset button. Press it once (don’t repeatedly press). Wait a few minutes to see if the system restarts.

If the furnace roars back to life—great! If not, it’s time to move on to the next step.

DIY Stops Here: When to Call a Professional 👷

Some problems just aren’t safe to tackle on your own. Here’s when you should call for emergency HVAC help:

• You smell gas or a rotten egg odor.
• The furnace makes banging, screeching, or grinding noises.
• Repeated shutdowns or a furnace that cycles on and off rapidly.
• Burning smells or you see smoke.
• No power after checking breakers and switches.
• Carbon monoxide detector goes off (leave the building immediately).

Briggs Heating technicians are NATE-certified, which means they’re trained to handle these risks safely and efficiently.

What Pros Do When They Arrive

Curious what happens next? A licensed technician will:

• Inspect the entire system, including electrical and gas connections.
• Use diagnostic equipment to check voltage, fuel pressure, and airflow.
• Test for carbon monoxide leaks using professional sensors.
• Review error codes, if your furnace has a digital display.
• Follow manufacturer and building code requirements for safe operation.

They’ll never skip safety steps—your well-being comes first.

Furnace Safety Warnings: What the Experts Say 🚨

• Electrical Dangers: According to OSHA, always kill power before opening panels—furnaces can carry lethal voltage.
• Carbon Monoxide (CO): The CDC reminds homeowners that CO is odorless and deadly—never ignore a detector alarm.
• Manufacturer Rules: Always follow the user manual and any tags/labels on your equipment.

Never bypass safety switches. They exist for a reason.

Maintenance: The Best Cure for Furnace Nightmares

A clean, well-maintained furnace is less likely to fail. Here’s what you can do:

• Change filters monthly during heating season.
• Schedule professional maintenance every fall.
• Keep vents and registers free from blockages.
• Listen for new noises—early warning signs matter.

Regular checkups can spot worn parts before they become a midnight emergency.

Time, Money & Peace of Mind: What to Expect

DIY checks can take 10–30 minutes. Calling for emergency HVAC help usually means same-day (or even within-the-hour) service, but that depends on demand and weather. Cost varies by the problem: replacing a filter is cheap; replacing a major part can be more. Typical professional diagnostics take one to two hours.

A quick fix may get you heat fast. But persistent issues? Let a pro rule out hidden dangers.

When It’s Truly an Emergency

Some heating failures can wait. Others can’t. Call right away if:

• Temperatures are dangerously low (risk of pipes freezing or health concerns).
• There are vulnerable occupants (infants, elderly, medical needs).
• There’s a strong odor, smoke, or you suspect a fire hazard.

Briggs Heating offers 24/7 emergency HVAC service. We’re ready any time—day or night.

Frequently Asked Questions

My furnace is blowing cold air. What’s wrong?

Check your thermostat first—make sure it’s set to “heat,” not “fan.” If settings are correct, a clogged filter or ignition problem may be to blame.

How often should I replace my furnace filter?

Most filters should be replaced every 1–3 months. If you have pets, allergies, or run your system constantly, check monthly.

Is it safe to relight the pilot myself?

If you’re comfortable and follow the instructions in your furnace manual, yes. If you smell gas or feel uneasy, call a professional.

Can I run my furnace if the carbon monoxide detector battery is dead?

No. Replace the batteries immediately. Never run fuel-burning equipment without a working CO detector.

Seasonal Tips & Local Considerations ❄️

Winter storms, power outages, and sudden cold snaps can all stress your furnace. Before the cold hits:

• Test your system in early fall.
• Keep a backup heat source available if possible.
• Know where your breakers and gas shutoffs are located.

Even in milder climates, rapid temperature swings can reveal hidden furnace issues.

If your furnace is still silent after these steps, don’t sweat it—Briggs Heating is always on call. Our certified team handles everything from AC repair near you to emergency HVAC fixes, 24/7. Stay warm, stay safe.

Call Briggs Heating now — or reach us anytime at  877-748-7966 .