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Furnace Troubleshooting

You may be in such a situation. The weather is cold and you arrive home to a cold house. Then, you ask the question: why is my gas heater not working? Well, there could be several reasons. The power supply may have gone. A circuit breaker may have blown or tripped. This article will look at these and various other reasons why your gas heater is not working.

Things To Check If Gas Heater Stops Working

Regular furnace maintenance helps maintain your heater system and prevents heater failure. However, if your gas heater is not working, here are some things to check.

Power Switch

You may have a furnace with an on/off switch. Have you switched it off by mistake? This is often the case, especially if you have some items you may have kept close to your heating system.

Similarly, you should check the furnace switch if you have had some home maintenance work done by repair technicians. For example, you may have had an electrician, plumber, light installer, or cable installer working near the furnace power switch in your attic.

Gas Valve

Your gas supply or fuel to the furnace could be open. Certainly, a break in the gas supply to your heating system can leave it without fuel. Consequently, the gas heater could stop working. So, trace the gas line from the gas heater back to the metre. If the handle is perpendicular to the gas pipe, turn it so it becomes parallel.

Fuse Box

An electrical breaker for your gas heater may have tripped. So, check the power supply. Perhaps, resetting the tripped breaker may get your gas heater working again. What if the power to the furnace continues tripping off? One likely cause is a safety feature being activated.

Call a licensed heating repair technician to inspect it. They can find out if it is a mere power supply, furnace safety, or electrical issue.

Safety Switch

Furnace safety switches are also called upper limit switches. They detect high temperatures and activate a shutdown of your furnace to prevent a fire. Examples of fire hazards include a faulty blower motor, capacitor, or control board. These can contribute to the air flow not working. These are common issues that a licensed repair technician can fix. For instance, they can help you reset the system after the furnace safety switch feature is activated.

Your furnace will not start if the vent safety switch is activated. The safety switch works by monitoring flue gases as they move through the heat exchanger and are released through the top of the roof.

When the vent is blocked by say a bird’s nest or a wasp nest, the vent safety switch can activate. Likewise, that chalky substance coming from the gas odorant can build up and block the vent. Moreover, this build up can lead to a misdiagnosis of a heat exchanger failure. That is why repair technicians may clean it off as part of your gas heater tune-up.

Error Code

Can you see any error codes? If yes, then check the error codes in your furnace user problem. This is how you can tell if it is a severe problem.

Pilot Light

The pilot light or ignition sensor can often be the reason for your gas heater not igniting. The furnace’s pilot light is a small flame. The pilots flame ignites the gas and the propane or natural gas in turn, heats the air in your home. However, if the ignition sensor is dirty, you have to clean it.

Interestingly, you can find similar pilot lights in water heaters, gas fireplaces, and old gas stoves.

Signs of a Faulty Pilot Light

The pilot light could blow out because of strong drafts. You would have to manually reignite it. However, remember to consult the manufacturer’s manual or owner’s manual. If this happens most of the time, consider additional attic insulation or insulating around your furnace.

The pilot light may burn orange or yellow. It should actually burn a crisp blue. That is to say, the amount of oxygen in the area is inadequate. Alternatively, it implies the flame is releasing carbon monoxide. This is a toxic emission and you may need a professional repair technician to fix it.

Checking the pilot light on the central heating system? Below are some steps to take:

  • First, remove the front panel or cover of the gas furnace. Now, you can see the burner assembly and pilot.
  • Second, try to relight the pilot light if it is not staying lit.
  • Furthermore, check the colour of the pilot light if it is burning.

What Else Should You Check?

Thermocouple or Flame Sensor

You can find the thermocouple version in older equipment. On the other hand, flame sensors are seen in modern furnaces. The thermocouple is a safety measure that detects a weak or non-functioning pilot light. It activates and shuts the furnace off thereby preventing an explosion.

Check the sensor by removing it with a screwdriver. Use some medium grain sandpaper to clean the sensor probe if necessary. However, you have to be careful so you do not break anything. When done, replace the sensor exactly as it was. Fix back the front panel and turn on the gas. Finally, turn on the heater.

Thermostat and Its Batteries

Is it simply that the thermostat is not working? If it does not seem to be working, you can trace the wires all the way to the furnace for breaks. Should you find one, splice the wire pieces back together. Then, wrap it with electrical tape. In addition, before your heater clicks on, ensure your thermostat is set to “heat” or “automatic”. When setting your indoor air quality, the temperature control selector has to be above the current room temperature.

Likewise, the fan switch should be on “automatic” mode (the blower motor operates only while the furnace is operating). You can as well set the fan switch to ON so that the airflow can run continuously. If you have a smart thermostat, it may get stuck. Simply restart it, but be sure to remove it from the wall as you do it. Once it’s done, reattach them so that they complete a manual reset.

Fixing your gas heater could be as simple as replacing your thermostat batteries. That is, if your thermostat has batteries.

Air Filters

Your home may have filters located in air vents or air filters in the furnace. Just like other electrical components in your home, clogged or dirty air filters can wear out your gas heater. It may not be able to take in enough air and enough warm air may not blow through the air vents.

Moreover, when filters are clogged with dust and dirt, the heat exchanger can overheat and shut off. Not only that, it leads to soot building up on the heat exchanger. Ultimately, the gas heater runs less efficiently. Therefore, you need to clean your air filters.

On the other hand, the blower may be running but no heat is being released. This is a sign that you should consider replacing the filter. Another sign is when you cannot see light through the filters clearly.

You should change your air filters every 1 to 3 months. Above all, follow the instructions in your owner’s manual. It can help you locate where the filter is and how to remove it. Remember, close the cover properly. If the furnace door is not well closed, your furnace may not turn on.


One worrisome sign you should watch out for is a smoky, burnt, or gas smell. If the gas heater is not on, there should be no smell in the air. If you notice any of these signs, invite a professional to check your system. Also, install carbon monoxide detectors and smoke alarms in your home.

This is a needed precaution if you own a gas-fired furnace. As it is working, the combustion produces carbon monoxide. The gas is odorless, which makes it extremely dangerous. Thus, if your carbon monoxide alarm goes off, everyone should leave the home and the fire department should be called.

Heat Exchanger

Normally, your heat exchanger helps keep various gases and liquids separate. Thus, it ensures your heating and cooling systems function effectively. Unfortunately, your heat exchangers can crack. This could be a result of old age or poor maintenance. This crack could result in the release of carbon monoxide which is a common by-product of gas furnaces.

As mentioned earlier, carbon monoxide is toxic and poses a health risk. A cracked heat exchanger cannot be repaired. Rather, it could be a sign of an out-of-date furnace. Consider getting a new gas heater.


The blower directs air from return ducts into the hot heat exchanger. If it is not functioning, in other words, if the furnace does not blow air, you may need a repair technician to replace it.

Insufficient Heat

Sometimes, the gas heater may be working but the heat produced is insufficient to warm the air in your indoor space. You need your HVAC technician to check if your HVAC unit is the right size for your home. Another thing to check for is clogged filters.

General Central Heating Systems Maintenance Tips

Granted, instead of getting several gas heaters for various rooms, you can make your gas heater a ducted heater system. That is to say, you are implementing a ducted heating system that consists of a gas furnace and ducting vents in the other rooms.

Here are some dos that you should perform for your ducted heating system:

  • Once a year, have the area around the furnace’s blower vacuumed. In addition, slide out the fan unit. Then, clean each fan blade using a toothbrush. Round it off by vacuuming with a brush attachment on a vacuum cleaner.
  • Similarly, check for oil ports on the motor. You may check for it near the motor shaft. To clean it, first remove the cover plate. Then, add two to three drops of non-detergent motor oil into each port. If your motor has oil ports and requires lubrication, then lubricate it once a year.
  • The blower motor may need a reset due to an overload. Check for the reset button close to the housing of the blower motor. If it is there, press it. However, if nothing happens, give it up to 30 minutes so the motor cools. Then, press the reset button again. If these measures fail, call in HVAC Technicians.

Reverse Cycle Air Conditioners Vs. Gas Heaters

Of these two heating options: air conditioning and gas heating, which is better? Here are a few pros and cons:

Advantages of Gas Heating

  • Gas heating is a relatively quick and efficient heating system.
  • It is a reliable power source, especially if your area has an unreliable electricity supply.
  • Natural gas is a cleaner burning fuel than certain forms of electricity generation methods. Besides, it releases around ⅓ of greenhouse gases.

Disadvantages of Using Natural Gas or LPG Heaters

  • It is quite expensive.
  • There is the risk of carbon monoxide poisoning. Gas heaters need to be serviced regularly and the room well ventilated.
  • When gas heaters are faulty, they can pose a fire risk. After all, gas is quite combustible.

Advantages of Air Conditioning

  • Air conditioners offer more savings as compared to gas heaters.
  • They feature advanced filtration systems that improve air circulation, catch dust and reduce the risk of respiratory issues.
  • They have a smart control option and energy sensors that let you turn on the heating system from anywhere. An example is when you are at work.

Hire A Professional Gas Repair Technician

You may have followed the furnace troubleshooting steps suggested above and seem not to get results. If that is the case, then get a furnace repair technician to examine your gas heating system. Perhaps the blower is faulty or the heating system is out of balance. You can have peace of mind they will handle all your gas heating issues whether it is your gas space heater or water heater not working.

Plumbing Services in Canberra

Blueline Plumbing & Gas are your local specialist for all domestic plumbing and gas fitting needs.

Get in touch for a quote or speak with a qualified plumbing specialist. We will help you find a solution for your emergency plumbing or plumbing repair needs.

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