How Do I Know If There’s A Problem With My Furnace?

Autumn is in the air, and your furnace is becoming more relevant as cooler temperatures roll through. Now is a good time to handle furnace issues so you’re prepared before Mother Nature really shows her teeth come winter. As you brush the dust off your furnace, we can’t help but wonder: do you know what to look for in a healthy furnace?

Until the technician arrives, here are some clear indicators of furnace trouble that should help give an idea of what to expect.


Your furnace is a complex machine with moving, stationary, and electronic parts. Over time, moving parts wear out. Expansion and contraction due to heat cause stationary parts to develop cracks. Corrosion occurs on electrical components. Age is just a number; a very important number when discussing furnaces. On average, a gas furnace should last anywhere from 20-25 years. The serial number on your machine should tell you its age. If it’s older than the usual lifespan, it could be time to consider purchasing a new furnace.

Abnormal or Incomplete Startup

Every furnace has a sequence it goes through in order to start, run, and heat your home properly. Sequences vary slightly from furnace to furnace, but in general, a typical heating sequence follows similar steps.

  1. The thermostat tells the furnace to turn on when the temperature in the house drops below setpoint.
  2. The exhaust inducer motor comes on and the furnace does a self-check to make sure it is safe to run.
  3. Once the self-check is complete, and it is safe to run, the ignitor heats up.
  4. When the ignitor is hot enough, the gas valve will open and the burners will fill with flames.
  5. Once the burners are proven to be ignited, and the internal heat exchanger heats up, the blower fan will be commanded on.
  6. During startup, safeties monitor each step of the process.  If at any point the safety mechanism alerts the control module to a failure in any step, the furnace will stop the heating sequence until the issue is resolved.  

The ignition system of your furnace may vary by the age and manufacturer. Regardless of the type of ignition you may have: Standing Pilot, Hot Surface, or Spark Ignition, all furnaces have some form of safeties that monitor the equipment during the startup.

Preventative maintenance by having your equipment cleaned prior to the start of the heating season will help you avoid the emergency call when the weather turns cold. Before it gets too cold, turn up the heat on your thermostat and check to see if your system is working properly.

Weird Noises

HVAC systems are not silent by any means. Some level of hammering noises is normal. But, if you hear exceptionally loud clunky or banging noises coming from your furnace, there may be a loose component that needs replacing or repairing. In forced-air furnaces, a blower motor is usually the clamoring culprit. Even the most skilled DIYers have trouble fixing their way out of this one, so it’s best to call the pros for an immediate fix.

Cold Air

A furnace’s one job is to heat your home. If it is not doing this and, on the contrary, delivering cold air, you know something’s up. Sometimes it is a simple circuit breaker issue; but, a furnace that’s using power but not producing heat is an issue that a certified technician should solve.

Higher Cost of Heating

As in business, a sure-fire way of detecting a problem is by looking at the bottom line. If your bill is showing higher heating costs than you’ve averaged previously, it could indicate that your furnace is running constantly or not heating properly to justify costs. Contact a professional for an inspection to clear up what’s going on.

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