Asked by: Monika Ciss
home and garden indoor environmental quality

Why is my pilot light not staying lit on my furnace?

Last Updated: 5th January, 2020

If your furnace's pilot light won't stay on, the furnace won't work. Some common causes include issues with the thermocouple and pilot tube. A faulty thermocouple may arbitrarily determine that the light is off when you want it on and vice versa. It could simply be that the thermocouple is bent.

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Herein, should pilot light always be lit on furnace?

If you have an older gas furnace, your heating unit relies on a little blue flame known as a pilot light to ensure ignition of the burners. Water heaters, gas fireplaces and old gas stoves also often have similar pilot lights. Since the pilot light needs to remain active, your furnace is always consuming some gas.

Similarly, how do you clean a thermocouple on a furnace? Use a screwdriver to loosen the screws and remove the thermocouple from the pilot assembly for cleaning. Use a piece of steel wool or the abrasive side of a sponge to gently remove the soot without damaging thermocouple. Avoid using cleaning products, especially those containing flammable chemicals.

Correspondingly, how do I know if my thermocouple is bad on my furnace?

If you can't get the flame to light at all, and you're sure the gas is on, there's probably an obstruction in the pilot tube. If the flame lights and goes out when you release the gas control knob after holding it in for the recommended 20 to 30 seconds, that's the sign of a thermocouple malfunction.

How much does it cost to replace a thermocouple on a furnace?

Cost to Replace a Thermocouple on a Furnace Replacing a thermocouple costs $150 to $250, mostly due to labor time. On older models without an ignitor, it checks to make sure your pilot light is lit. If it's not, it'll shut the gas off.

Related Question Answers

Hakkoum Ochs

Professional

Is it dangerous if your pilot light goes out?

Can a Pilot Light Outage Be Dangerous? The worry here is that when a pilot goes out, the gas valve that supplies the fuel for the pilot flame could still be pumping gas. This can mean a buildup of gas, and when the pilot is relit or relights itself it could result in a very serious explosion.

Estrellita Cantarero

Professional

Should you turn off furnace pilot light in summer?

My short answer is that yes, you should turn off your furnace in the summer. Let me elaborate. It's important to know that your furnace will continue to consume energy all summer if it's left on. The pilot light on gas furnaces, for instance, will burn gas around the clock.

Karren Valverdinho

Professional

Can you test a thermocouple?

Select the ohms or resistance option on your multimeter. Place one test lead on the side of the thermocouple and the other to the end that screws into the gas valve. If the thermocouple has proper continuity, a small resistance reading should be visible on the multimeter.

Ihor Gary

Explainer

Can a pilot light cause carbon monoxide?

Carbon monoxide is a colorless, odorless gas produced during burning fuel. It doesn't leak from a pilot light that's gone out, but if the light keeps going out even after you relight the pilot, it can indicate that you have other problems.

Bethsabe Katarain

Explainer

Should I turn the pilot light off?

Turning off the pilot lights on gas fireplaces and furnaces when not in regular use can save energy and money. If you switch your pilot light off, your air conditioner won't have to work as hard to reverse the heating effect of the pilot light. Your furnace only uses a small amount of gas to power the pilot light.

Shaowei Boquera

Explainer

Do I need to turn gas off if pilot light goes out?

This system will allow a small amount of gas to leak through the pilot tubing. If the pilot light is out, the gas must be shut off at the appliance isolation valve, normally located in close proximity to the appliance. Then you can follow the manufacturer's instructions to relight the pilot.

Benedetta Pallavan

Pundit

How long should a thermocouple last?

The thermocouple unwinds and switches on the fireplace. Thermocouples are rigorously tested and should last for years. Indeed, experts believe a four-year check cycle is all that is needed to make sure things are functioning properly.

Maraya Jabbie

Pundit

What does a thermocouple look like?

The thermocouple looks like a piece of metal tubing smaller than a soda straw. To find it, first locate the gas control box. This is the box that the main gas line enters, where you turn the gas on in the furnace. The other end of the thermocouple sits in the flame of the pilot light.

Wasima Pottgen

Pundit

What causes a thermocouple to fail?

Changes in temperature can cause regular expansion and contraction in metal, which will cause thermocouples to weaken over time. After enough time, metal fatigue can cause a thermocouple to break.

Chaimaa Zaforteza

Pundit

How much does it cost to replace a thermocouple?

Thermocouple Replacement - $20-$150
Calling a professional plumber to install a new thermocouple should only be up to $150. If you do the work yourself, you will only pay the price of the part which is about $20.

Irenea Viola

Pundit

Will a pilot light stay lit with a bad thermocouple?

A thermocouple senses the heat of the pilot and allows gas to flow to the burner. A bad thermocouple will shut off gas to both the pilot and the burner so the pilot light won't stay lit.

Corrie Levita

Teacher

How do you test a thermocouple on a furnace?

Steps
  1. Locate the pilot light controls on the gas valve.
  2. Turn the pilot light on for 30 seconds.
  3. Release the button to see if the pilot light goes out.
  4. Turn off the gas supply to test the thermocouple again.
  5. Count to 20 and wait for the pilot light to go out.
  6. Listen for clicking near the gas valve.

Sadako Gassa

Teacher

Can you clean a thermocouple?

If the Thermocouple is faulty it will cause the unit to shut down. How to clean? Remove Thermocouple from pilot assembly, using steel wool or emery cloth to lightly clean the tip removing any soot or build up that might have accorded due to an improper pilot flame.

Ramiro Quagliano

Teacher

Can a thermocouple be repaired?

The thermocouple, which operates as a safety device, turns the gas supply off when the pilot light goes out. A burned out or broken thermocouple should be replaced. To replace a thermocouple: Step 1: Unscrew the copper lead and the connection nut inside the threaded connection to the gas line.

Donato El Yemlahi

Reviewer

How do I test my thermostat?

Thank goodness it is much less expensive to replace a thermostat than your central heat and air unit.
  1. Check your thermostat to make sure it is in the "On" position.
  2. Stand at the thermostat while an assistant stands at the furnace.
  3. Raise the thermostat heat settings slowly.
  4. Turn off the breaker to your furnace.

Abdeloihid Rigueira

Reviewer

Can a pilot light flame be adjusted?

Adjusting the Pilot Flame
If the pilot flame is too small, you may be able to make it larger by turning the pilot adjustment screw on the valve control counterclockwise with a screwdriver to open it. The cause of a weak flame may also be an obstruction in the pilot tube.

Nazmul Broughton

Reviewer

Can hear your furnace click on but it does not fire up?

The Pilot Light (Faulty Ignition Sensor) The pilot light or ignition sensor is usually the most common issue when your furnace will not ignite. This is typically the problem if you can hear your furnace click on but it does not fire up. If the sensor or ignitor is dirty, it will need to be cleaned.

Xiaojie Edesa

Reviewer

How do you clean the ignition sensor on a furnace?

Once you have removed the sensor, gently rub the metal rod (and nothing else) with a very light grit sandpaper. Remember, you're not sanding down an auto body here, just ridding the sensor of any buildup. Then, use a clean paper towel to wipe clean any dust left behind by the sanding.

Kendra Matibe

Supporter

Where is the reset button on a furnace?

The reset button is typically located inside the blower compartment on the side of the blower motor. When should I press the reset button? First, you need to locate your circuit breaker and switch off the power supply to the furnace. Then, if you see that the button is up, push it to reset your furnace.