Modern furnaces are impressive appliances that come with several components for accurate and durable performance. Unlike older models, modern models are less noisy, more accurate, and a lot more dependable. And the list of impressive features is the main reason.
But the numerous features and components also make the reason for which furnaces develop issues, mainly when not professionally serviced or maintained. Some of the problems have effortless solutions, whereas others will require professional repair/servicing.
If you’ve paid any attention to your furnace by now, you may have noticed that specific steps are necessary for proper operation. When everything works fine, the thermostat gives the heat request to the furnace (you hear the “click”), and soon enough, you hear the blower running. The furnace will ignite, and you should feel hot, warm circulating inside the house any time soon. What if everything goes fine, but your furnace doesn’t ignite?
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What should you do if the furnace doesn’t ignite?
One of the many challenges of modern furnaces is that there could be several problems causing that symptom once a symptom occurs. When your furnace doesn’t ignite, several things could go wrong, so you should check each of them to figure it all out. Even if you’re not going to be able to fix it, you could at least give the HVAC technician some heads up about what’s wrong with your Luxaire furnace.
Examine if you have a gas supply
When your furnace doesn’t ignite, one of the first things to do is check the gas supply for your furnace.
Should you be on the city gas line, you won’t be able to check the gas supply as it’s too dangerous. Call the HVAC technician for investigation. If you sense gas smell near the furnace, it’s a good thing; it means that you don’t deal with the gas supply, so you should look for other possible causes for the furnace not igniting.
If you’re using propane/lp gas for your furnace, it’s a lot more comfortable verifying the supply. Go outside and see where the gas storage tank is. You should notice a domed area in the top center of it; it’s where the fill valve and the gas pressure gauge should be.
You’re not dealing with gas supply issues if the pressure gauge reading is at least 25. If it’s lower, you have to call the gas company for a fill-up. Call the HVAC technician only after eliminating the gas supply issue from the list.
Once you turn on the furnace and set the thermostat to a higher setting, specific actions should take place, helping the furnace ignite. The furnace fan collecting air into it for initiating the burning process is the first sound you hear, whereas the swoosh sound of the gas igniting will be the next. It shouldn’t take longer than a couple of seconds until you observe hot air coming out of the vents inside your house.
If the thermostat isn’t correctly operating, none of these actions will take place. The thermostat is defective if any of these actions didn’t take place. Everything will be dead silent.
Replacing the thermostat is relatively straightforward. If it’s battery-operated, replace the batteries, as they could be drained out or damaged. Universal thermostats are available, but you should double-check with an HVAC technician for the best guidance.
The gas furnace will burn a combination of air and natural/LP gas. When the air in the system isn’t correctly circulating, the furnace won’t generate the necessary air and gas combination so that the furnace won’t ignite.
But it doesn’t always have to be a broken component as the cause. Sometimes, air filters are clogged and block proper air circulation. Filters do get dirty, which is why cleaning and replacing are required. A dirty/clogged air filter doesn’t make the most severe problem on a furnace, but it’s enough of an issue to stop the furnace from igniting.
Source of the ignition
Older models would use a pilot light for lighting the gas/air mixture; modern models come with an electronic ignition system. When it doesn’t do the job, the furnace doesn’t ignite.
With pilot light, a tiny flame would run continuously inside the furnace. It doesn’t practically use a lot of gas. Examine the bottom of the furnace, and look for the burners. The pilot light should be placed to the side of the tray, a bit above it. If it’s not lit, you may use a long match and attempt to light it. If it still doesn’t light, you will need to go further with investigations.
If your furnace has electronic ignition, you should find the igniters in the same place as the pilot light. The modern igniters are made with lightweight metal alloy, becoming very hot as electric current goes through it. A clicking noise means that the furnace attempts to fire. However, when the clicking repeats several times, it means that the igniter doesn’t come on nor working. Try to reach the igniter and carefully clean it and the area around. Carbon may build up, blocking the sensitive points and the furnace from igniting.
Should you call the technician?
If you’ve tried all actions and none of them gave results, you should call the HVAC technician. Sometimes, in-depth problems could make the furnace not ignite, and only the professionals will solve it.
Luxaire furnace won’t stay lit- what’s the cause?
There are various types of furnaces out there, and they present some differences in terms of ignition systems. However, the main steps for the heating process are as follows:
- The thermostat sends a request for heat.
- The draft inducer fan begins to run. The fan will collect and take fresh air into the furnace, to create a safe combustion chamber.
- The gas valve will open, sending gas to the pilot burner.
- An electronic spark will light the pilot light.
- The flame sensor informs the furnace that the pilot was correctly lit.
- The gas valve will send gas to the burners that the pilot light just lit.
Some furnaces come with direct ignition, so they don’t have a pilot light. They skip steps from 3 to 5, lighting the burner directly. The furnace still comes with a flame sensor, but it’s placed over the burner’s flame.
For furnaces with standing pilot light, step no.4 won’t take place. You light the pilot light before any steps take place. Keep in mind that these are old furnaces, so you may want to upgrade and get a new furnace.
Sometimes, the pilot light will light, but it will go out before lighting the burner. The causes are several:
Poor flame sensor placement
The flame sensor could be just fine, but it’s not placed correctly, so it’s impossible to identify the pilot’s flame.
Faulty flame sensor
The flame sensor is supposed to inform the furnace that the gas is lit. The furnace won’t be able to continue to let the gas flow into your house if the flame sensor doesn’t work, even if the pilot light was out.
Sometimes, flame sensors get faulty, and replacement is the only solution. You should call the HVAC technician for the job.
Poor gas pressure
When there’s not enough gas getting to the pilot light, it won’t help the thermocouple work correctly. Adjustment or replacement of the gas valve could be necessary. Again, call the technician.
Faulty ignition board
The tiny computer control board controlling the gas flow, spark, and all other ignition cycle steps may have become defective. You cannot fix it, so replacement is the only solution.
A piece of thought on standing pilot lights
When you’re attempting to light a standing pilot light on an old furnace and still go out, you should ensure that you’re pressing the pilot button for the right amount of time.
After lighting the pilot, you will have to maintain the button depressed for more than 30 seconds (up to a minute, even). It will provide the flame the time to heat the flame sensor telling the furnace that it’s time to light the burner.
Here are possible causes when you still don’t succeed in keeping the light on:
- Bad limit switch, in which case replacement is needed
The furnace comes with a limit switch that stops operating when the heat exchanger gets too hit. Closed/blocked vents, dirty filters, and various blockages in the airflow make typical furnace overheating causes.
- Defective thermostat
The thermostat may incorrectly inform the furnace that the home is warm, shutting off the burners before actually reaching the set temperature.
- Defective flame sensor
In direct ignition furnaces, the flame sensor is placed over the burner, shutting off the gas when it doesn’t identify the flame. If the flame sensor is faulty, it won’t turn on gas whenever there’s a call for heat.