Gas furnaces are much more complex than most people realize and have many different components that all need to work properly for the furnace to run and heat effectively. Over time, these components can wear out or malfunction, leading to the furnace not working or not heating effectively. Issues with the thermostat or a dirty air filter can also affect a heating system’s performance or cause various problems with a furnace. In this article, we’ll take you through some basic steps for troubleshooting common furnace issues so that you can identify serious or dangerous problems and when to call for professional help.
Furnace Doesn’t Come on When It Should
Having your furnace fail to turn on can be incredibly frustrating and is an issue that you’ll want to have an HVAC technician check out immediately. While the Shreveport area normally doesn’t get cold enough that you need to worry about your plumbing freezing, your house can still get uncomfortably cold quite quickly if your furnace isn’t running.
Many issues will cause a furnace to fail to start, such as an issue with the thermostat not signaling it to run. If the problem is with your thermostat, the batteries could be dead and need to be replaced. As such, this is the first thing we’d recommend checking because you simply might need to replace the batteries in your thermostat. It’s also a good idea to check that the circuit breaker that controls the power to your HVAC system isn’t tripped. If the batteries in your thermostat are still good and the breaker isn’t tripped, you’ll need to have a technician troubleshoot your furnace since numerous issues could prevent it from running.
One common issue that can prevent a furnace from turning on is that the pressure comes loose or gives out. The pressure switch works to ensure the inducer fan is pulling air into the combustion chamber and creating a draft so that the combustion fumes get drawn outside. The first thing that happens when a furnace starts up is that the draft inducer fan starts running. The pressure created by the fan triggers the pressure switch to close. As soon as the switch closes, it signals the control board to open the gas valve and turn on the electronic igniter so that the burners light. If the pressure switch is faulty or the inducer isn’t working properly, gas won’t ever start flowing and the furnace won’t light.
Another possible reason that your furnace won’t turn on is that the electronic igniter is dead. Most newer furnaces use a hot surface igniter similar to a light bulb filament. When the furnace needs to turn on, the igniter almost instantly becomes red hot and the heat radiating off of it ignites the burners. This type of igniter often only lasts for three to five years since it can eventually end up cracking due to it continually heating up and cooling down.
Furnace Shuts Off Too Soon
When a furnace is working properly, it should keep running until the house reaches the temperature the thermostat is set to. If your furnace often shuts off before reaching the right temperature, you may have issues with it overheating or a malfunctioning component, such as the pressure switch or flame sensor. Overheating most commonly occurs due to a dirty air filter so the first thing to do in this situation is make sure you don’t need to change the filter. The issue when a furnace filter is dirty is that it greatly reduces how much air the blower can bring in. If there isn’t enough cooler air continually flowing over the furnace’s heat exchanger, it can quickly overheat and trip the temperature limit switch causing the furnace to shut down.
The flame sensor in a furnace also often only lasts for around five years since it is exposed to extreme heat whenever the furnace is running. If the flame sensor gives out completely, you’ll end up with your furnace continually trying to turn on but never staying lit for more than a few seconds. The flame sensor keeps the furnace lit and prevents gas from flowing if the burners aren’t lit. A flame sensor can also sporadically stop working as it begins wearing out, leading to the furnace occasionally shutting off before it should. This can also happen if the sensor is dirty, which is one of the many reasons why you should have your furnace maintained and cleaned annually.
Furnace Doesn’t Heat Effectively
If your heating system isn’t putting out much hot air or your furnace takes much longer than usual to bring your house up to temperature, the first thing to check is the air filter. Simply replacing the air filter if it’s dirty can greatly improve airflow and enable your furnace to perform effectively. Contact a technician if the filter isn’t dirty or changing it doesn’t fix the issue. If your furnace is fairly old, it may simply not be able to work effectively any longer and will need to be replaced.
A technician will also check the condition of the burners and the color of the flames they produce when a furnace isn’t working as expected. The burners should always produce a steady, bright blue flame. If the flames are weak or flickering and are orange or yellow, the gas isn’t fully combusting and the flames are producing far less heat than they should. In many cases, all the technician will need to do is clean the burners to fix this issue. However, incomplete combustion can also occur because the inducer isn’t pulling in sufficient air, resulting in the flames essentially being starved of oxygen. In this case, the solution is often to replace the inducer.
Furnace Makes Loud or Unusual Noises
Unusual sounds like squealing, screeching, or grinding when your furnace is on, usually indicate an issue with the blower, and it might need to be repaired or replaced. For instance, the bearings in the blower motor often create a screeching sound when they start to wear out. This noise isn’t something you want to ignore since the motor will eventually burn out if you don’t get the bearings replaced.
A rattling sound can indicate a much more serious problem as it often indicates a crack in the furnace’s heat exchanger. The reason this is such a serious issue is that it can result in carbon monoxide escaping and mixing with the hot air that the blower circulates throughout the house. As such, we always recommend shutting your furnace off and calling for an immediate inspection if you hear it rattling.
In some situations, a furnace might make a loud booming sound as it lights. This sound indicates an issue preventing the burners from lighting immediately when the gas valve opens. This delay in ignition results in gas filling up the combustion chamber and essentially producing a small explosion or fireball once it lights. This is also not an issue you should ignore since the fireball has the potential to damage various components.
If your furnace has any issues and you need the help of an experienced HVAC company in the Shreveport area, Bobby L. Greene Plumbing, Heating & Cooling Co. is the one to turn to. We’ve been providing residential and commercial heating, air conditioning, and plumbing services since 1959 and can quickly determine what issue your furnace has and how to fix it. We also offer reliable HVAC maintenance services that can help to prevent most HVAC issues from occurring. To schedule a furnace inspection or any other service, contact us today.