What to Do If the Pilot Light Is Lit But the Furnace Won’t Kick On?

Learn what could cause the issue and it can be fixed.

Written by Camilla Moln. Updated on What to Do If the Pilot Light Is Lit But the Furnace Won’t Kick On

Having any issues with your furnace can drive anyone crazy while their homes stay ice cold! And when your water heater pilot light remains lit but burners won’t ignite, this is definitely the sign that something went wrong.

If you had to face this problem, we bet you have an older model of the water heater since modern boilers normally don’t have pilot lights to start the unit.

And if you have already tried all possible measures and methods in order to solve this mind-twisting riddle, but you still can’t make your furnace work as it should be, here we come for your rescue!

See, the most common reason why something like this can happen is that you have a failed automatic shut-off. However, this is not the only cause.

This is why today you will learn more about this issue and how to troubleshoot it yourself. In particular, we will tell you what factors may lead to such a malfunction, as well as what to do in case your boiler’s pilot light won’t ignite.

With this guide at hand, you will easily cope with the matter and have your whole home warm and cozy again!

Pilot Light Works But the Burners Won’t Ignite. What Is the Problem?

If your gas water heater’s pilot light is on, but not the burner, there might be different reasons for that. For example, you might have a failed automatic shut-off. Or, as an option, it could be a defective gas valve, or a rusty thermocouple. Any of those may lead to the pilot light being on but the burners staying dead.

However, all the reasons we have just listed here are just assumptions. To be able to define for sure what is going on with your furnace, you need to know all the other culprits that hide behind this problem.

Like this, you will be able to decide what solution you need to provide in each particular case to solve each particular case.

This is why below we are going to provide you with the list of the most common culprits that may lead to your furnace work issues.

Since multiple reasons are responsible for your furnace burner not igniting properly while the pilot light is still lit, you need to be aware of each and every one of them. So stay with us till the end and see what reasons can be found behind this issue!

Pilot Light Works But the Burners Won’t Ignite. What Is the Problem
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Check the Ignition Sensor

If your pilot light is lit but the burners won’t ignite, you might need to check the ignition sensor. A dirty sensor could be the reason why your furnace won’t stay on or even why your furnace won’t stop blowing cold air!

See, the working mechanism of this unit is the following. Only if the furnace’s heat exchanger (the part that actually heats the air) senses an ignition, will it power on the furnace.

However, dirt or grime can inhibit the sensor’s abilities. A trusted furnace repair company can carry out a furnace flame sensor replacement and the cleaning it needs to function properly.

Check the Ignition Sensor
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Inspect the Furnace Pilot Light

If you notice that your water heater’s pilot light remains lit, but its burners still won’t ignite, you might want to start by switching the furnace’s power on and off.

If after resetting the pilot the gas furnace still won’t turn on, you will have to power down the furnace and inspect the element for any damage.

If all the other methods and approaches fail, the best thing you can do is to call a professional to come and perform gas furnace maintenance as soon as possible. Remember that having problems with gas supplies can be dangerous for your health and even life!

Furnace Not Working - The Most Common FixFurnace Not Working – The Most Common Fix

Check the Electrical Panel

In case your gas water heater’s pilot light is working and it remains lit, but not the burner, make sure that the circuit breaker panels and the furnace itself are in the “on” position. Sometimes a simple solution like this is an answer to why your furnace won’t kick on.

However, if not in the “on” position, pop the breakers back into place carefully. Be sure to close the furnace door so the safety switch can activate the furnace.

Check the Electrical Panel
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The Gas Control Valve Might Be Defective

If the gas control valve of your water heater is not working properly, your burner won’t ignite. Because of the defective gas control valve, the main burner will not be able to light as the electronics in the valve fails to recognize whether the pilot light is lit.

Unfortunately, you can’t fix it if the problem is within your gas control valve.

You can find any serviceable parts in the market of course. But usually, you will need to replace the whole assembly.

The Gas Control Valve Might Be Defective
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Check For the Corroded Burner Line And Jet

There is no need to replace the whole unit unless you check the main burner, line, and jet.

The main burner won’t usually ignite if its line and jet get corroded with dust, debris, and dirt. So as a solution, we recommend you remove the burner from your water heater first.

Then, inspect its line and jet carefully.

If you see that the burner and the jet got covered with rust, what needs to be done is that you take an air compressor and blow that corrosion and rust away.

Check For the Corroded Burner Line And Jet
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The Automatic Vent Might Be Closed

Whether you own a gas boiler or a water burner, most of them have vents. And if those remain closed, your water heater simply won’t ignite! Moreover, most gas burners have two switches, one is a flame roll-out switch and another is a flue gas spill switch.

If they get faulty, the main burner also doesn’t light.

So what you need to do is to make sure that the automatic vents of your burner are open.

It will be an easy fix if your boiler won’t turn on due to the closed vents.

Also, don’t forget to check out the switches of your gas or water heater. If any of them work improperly, replace them with a new one.

The Automatic Vent Might Be Closed
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It Might Be a Rusty Thermocouple

The burner won’t light if the thermocouple gets rusty or covered with heavy corrosion. When the thermocouple gets corroded, it can affect the temperature as a result. Consequently, it doesn’t let your burner work properly.

The easy fix of this issue will be to remove the rust and corrosion from the thermocouple by simply cleaning them off with a vacuum. You can use a vacuum with a brush attachment as well in order to brush away dirt and debris from on and around the thermocouple.

However, we would like you to keep in mind one simple thing: the burner area will be extremely hot!

This is why, before vacuuming the thermocouple, make sure the unit is completely cool. Otherwise, there is a chance of fire hazards and burns on your skin as well.

After cleaning the thermocouple, don’t forget to replace it. And in case cleaning doesn’t work, have a new thermocouple and replace it. And remember, sometimes you may find, after replacing the thermocouple, that the pilot still doesn’t ignite.

This can happen sometimes and this is quite normal. In such a case, you can read our solution guide on pilot light won’t stay lit after replacing the thermocouple.

Now that you know what could be the reasons for the improperly working burner of your water heater, we hope it will be easier for you to cope with any flaw in the work of this appliance.

It Might Be a Rusty Thermocouple
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What If My Thermostat Won’t Kick On The Furnace?

Thermostat may also experience troubles with kicking on the furnace. However, in this case, the possible reasons will be somewhat different in comparison to those that lead to the similar malfunction of the burner.

For example, among the most common reasons we can list extreme temperatures, wonky wiring, dust buildup, and some others.

But all of them will anyway leave your thermostat unable to work properly and thus regulate the furnace heat level.

So we suggest you take the following tips into account and use them for checking what could be the problem.

What If My Thermostat Won’t Kick On The Furnace
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Try to Check the Batteries

If the thermostat is not indicating that it is powered on or won’t kick on the furnace, the problem might be with the batteries. See, the batteries might have simply run out of juice and need a replacement.

If your furnace is not heating your house at consistent times, switching to AA lithium batteries instead of alkaline batteries can extend the life and consistency of your system.

Try to Check the Batteries
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Check the Position Of Your Thermostat

If your constant chills are making you question why your furnace won’t go above 60, make sure your thermostat is in the heating position.

Even changing the physical location of your thermostat away from sunlight and/or drafts will ensure a more accurate reading of the thermostat and heating experience.

Like this, you will be able to spot the issue early enough to get it properly fixed.

So, now you are fully informed about everything that one may need for being able to cope with any more or less serious problem that comes with starting the burner or that comes with the pilot light work.

With the help of these tips and recommendations, we hope that your home will always be warm and cozy!

Frequently Asked Questions

⭐ Do all gas furnaces have pilots?

No. Modern models usually don’t.

⭐ Can a bad thermocouple prevent a pilot from burning?

Yes, it can do that.

⭐ Why is my gas fireplace not coming on?

Check the breakers box. If the breakers get tripped, your gas fireplace will not come on.

Written by
Camilla is an experienced Consultant with more than 20 years of preparing professional articles for numerous online resources. She has done a tremendous job and has learned a lot during her career. Camilla will advise you on the latest trends and give amazing tips on how to decorate a house.
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