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What Causes a Furnace to Stop Working? Learn How to Fix Common Furnace Issues


broken furnace

Your furnace is integral to your home. What happens if it breaks? What causes a furnace to stop working? We’ll explain the most likely answers to these questions (and what you can do about the problem) below.

Why is There Water Coming out of My Furnace?

There could be a few reasons, depending on the type of furnace you have.

High Efficiency Furnace

If you have a high efficiency furnace the problem most likely lies in either the condensate pump or the condensate drains.

1. If the condensate pump, or humidifier is broken, you will need to get it fixed by a professional.

2. If the condensate lines are clogged, call in a professional. If the lines have a leak, you’ll need to have them replaced.

Non-Condensing Furnace

If there is water coming out of your non-condensing furnace, there are three main culprits:

1. An improperly designed vent pipe: Inspect your flue pipe. If there is water leaking from it, or there isn’t a slope, you should contact a professional. They will inspect the vent pipe to make sure it is suitable, while also fixing any leaks.

2. Leaky humidifier: Look for leaks and clogs in your humidifier. Check the water tap line, drain line, water feed tube, and the outside casing of the unit. If it’s leaking or clogged call in a professional.

3. Leaking when the AC is on. Look at the condensate line to try and find the source of the leak. Then contact an HVAC professional to fix it.

Why is Your Furnace Heater Fan Not Working?

Try these steps if your furnace blower isn’t working properly:

1. Your furnace breaker may have tripped: If it has, reset it and allow time for a normal heating cycle.

2. Check that your thermostat is set appropriately: Too low and you may be cold, but the furnace might think the temperature is fine.

3. Check the furnace filter: A clogged filter can drop airflow, causing your home’s ductwork to shake and restricting heat going into your home.

4. Furnace flame colour should be blue: Red, yellow or orange indicates dust and dirt build-up in the burner.

5. Test the blower motor: Turn the furnace off and turn the thermostat to ‘fan only’. Wait a couple of moments. If you see or hear the fan turn on, your blower motor is fine. If not, you may have a wiring issue or motor problems. Call in the professionals to help with this one.

Common Furnace Noises


The motor could buzz due to a broken capacitor. It’s easy and inexpensive to replace. It can also buzz if blown or burned out, in which case it will still need to be replaced.


When your furnace turns off, hot metal parts can make a crackling sound as the surfaces cool down, which is normal. However, this noise may also indicate a problem. This sound needs the advice of a professional.


Dirt build-up in the burners can delay ignition and cause gas to build up. When it ignites you may hear a loud pop or bang sound, which can damage your heat exchanger which can be expensive to repair.


Your motor may not have enough lubrication. The sound could also mean that motor failure is likely. If the hum happens when the motor is slowing down, it could indicate a more serious problem.


This noise could indicate a faulty flame sensor, or a problem between the ignition and the gas. It will need immediate attention.

Find Out Why Your Furnace Stopped Working with Advice from Anchor Home Comfort

These are just some of the issues that can occur. If you’re unsure about what caused your furnace to stop working, don’t hesitate to contact the professionals. Contact Anchor Home Comfort for all your furnace needs.