How To Troubleshoot A Furnace That Won’t Start

A man checking a thermostat in a St. Cloud, MN home.

Brrr… It’s getting cold! You need heat, and your furnace won’t start. Now you’re wondering if there is anything you can do to get it started without having to call for help. 

It’s okay, you’re not alone, and thousands of Minnesotan homeowners having furnace problems right now are thinking the same exact thing! Fortunately, just because your furnace won’t start doesn’t mean you need to give us a call for a professional furnace repair. You might be able to get it started yourself.

Since 1947, at Neighborhood, our furnace repair experts have helped thousands of homeowners identify the cause of their furnace problems. Because we service all brands, there’s not a furnace on the market that we don’t know how to fix. However, just because we know how to repair any furnace doesn’t mean you need our help. 

Take a quick run through the following checklist first, and you just might be able to get heat again!

The 8 Step Can Checklist

When your gas furnace doesn’t start, your first instinct might be to reach out to a professional HVAC technician for help. However, there are a few common problems that you can troubleshoot yourself. Are you ready to learn how to troubleshoot furnace issues? Let’s dive into the seven steps you can try when your furnace won’t turn on.

Step 1: Check The Thermostat

When your furnace won’t run like it’s supposed to, don’t panic! Instead, check your thermostat. First, make sure you’ve got some fresh new batteries in your thermostat. This is one of the quickest and easiest furnace troubleshooting steps—and the only one that you might need.

Next, turn it to “heat” and adjust the temperature so that it is higher than the ambient temperature in the room. Once the thermostat is set to “heat” and the temperature is turned up, does the furnace start?

Yes – Great! You’re good to go.

No – Continue to Step 2.

Step 2: Check the Furnace Filter

It’s time to inspect the furnace air filter. HVAC systems have air filters, and if these filters are neglected and become dirty, they can lead to a whole host of furnace problems, including:

  • Decreased efficiency
  • Reduced airflow
  • Heat exchanger overheating

It’s crucial to change furnace filters at least every 30-90 days to avoid clogs. 

Did replacing the filter do the trick?

Yes Nice! That was easy. Bring on the heat!

No – Continue to Step 3.

Step 3: Check The Power

Just like most home appliances, your furnace needs power too. Make sure the circuit breaker for the furnace hasn’t tripped. Regardless of if you have a natural gas or propane furnace, circuit breakers control furnaces. 

If your furnace has a power switch, make sure it’s turned “on.” Now go back to the thermostat and turn it up again. Did it start?

Yes – Great job troubleshooting why your furnace won’t turn on!

No – Continue to Step 4.

Step 4: Check The Blower Compartment

If you’ve checked the circuit breaker and your furnace won’t turn on, it’s time to inspect the heating system’s blower compartment. 

Most blower compartments at the bottom of a furnace have an inspection window that you can look through. Inside you’ll see a circuit board with LED lights. Take a peek. Do you have green flashing lights?

Yes – Continue to Step 5.

No (They’re RED) – Uh oh. You should probably call for professional help. When you see red flashing lights, that means you have technical problems, and we all know that technical problems are usually best left to a pro. The experts at Neighborhood are here for your HVAC in St. Cloud, MN.

Step 5: Check The Drain Line

Usually, more towards the top of your furnace, you should be able to find a drain line. If that line is blocked, your furnace won’t turn on. If you have a condensate pump that’s not working, your furnace won’t start either.

Is the line free and clear?

Yes – Continue to Step 6.

No – Clear the drain line and repeat Step 1.

Step 6: Check The Gas

Sometimes getting your furnace to start could be as simple as making sure the gas is turned on. Follow the gas line from the side of the furnace until you find a shutoff valve and make sure it is open. 

Is it open?

Yes – Give us a call, because you’ve got a bigger problem.

No – Open the valve by making sure it is perpendicular to the gas line and repeat Step 1.

Step 7: Check the Pilot Light

If you’re still wondering why the furnace won’t turn on, turn your attention to the pilot light. Many furnaces have pilot lights, and the furnace won’t function properly if the pilot light won’t ignite. Your heating system’s pilot light is a safety feature that helps prevent gas leaks and will turn off if the flow of gas is interrupted.

You can shut off your furnace and relight the pilot light yourself if you’re comfortable performing some DIY work. With a gas furnace, you’ll need to make sure the gas valve is set to “pilot” while you’re relighting the light. 

If this is outside of your comfort range, you can always contact a professional for help with your HVAC in St. Cloud, MN.

Were you able to inspect and/or relight the pilot light?

Yes Go back and repeat Step 1. 

No – Call a professional!

Step 8: Check the Flame Sensor

When your heater furnace won’t turn on, you can check the furnace flame sensor. The flame sensor (or ignition sensor) is a safety feature that keeps track of when the heating system is burning gas. When the flame sensor can’t detect a flame, it will turn off your furnace to prevent a gas leak.

There are a few reasons why the flame sensor might not be working properly, including a buildup of dirt and grime. You can clean the flame sensor yourself, but you will need to first power down the furnace. 

Did cleaning the flame sensor restore heat to your home?

Yes Congrats! Enjoy the cozy comfort of home.

No – Call for help before you freeze in the cold.

My Furnace Still Won’t Start! What Next? 

Knowing what to do if your furnace won’t turn on can feel overwhelming. After you’ve run through these troubleshooting steps and still can’t get your furnace to start or are unsure what to do next, contact us.

At Neighborhood, we have an expert furnace repair team that has the knowledge and tools to check and fix all furnace models and brands. Our furnace repair technicians are certified to work with gas, water, and electricity. We know how to work with any heating system in a safe and efficient manner.

Our experienced professionals are available 24 hours a day, 7 days a week, to help identify the cause of your problems. We also offer 24-hour emergency furnace repair service throughout Minnesota. If you need help or have any questions about your furnace or would like us to come to your home and identify the cause of a problem give us a call, we’d be happy to help.

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