A faulty, misaligned, dirty, or damaged thermocouple is often the culprit behind your pilot light going out. The thermocouple is an automatic safety shutoff device that prevents the gas valve from opening if the pilot light is out.

How do you fix a pilot light that keeps going out?

Dirty Thermocouple



If it’s filthy shut your gas off so that the unit can cool down, then gently clean it by carefully rubbing it with fine grain sandpaper. When you’re done, simply turn the gas back on and light the pilot again. If dirt or grime was the issue, your light shouldn’t go out again!

Why won’t my pilot light stay lit on my heater?





If your pilot light won’t stay alight, it might be the thermocouple. Sometimes dust buildup collects on the thermocouple and blocks the sensor. Try cleaning the thermocouple and then relighting the pilot light. If it continues to go out, the thermocouple might need to be replaced.

Should thermostat be on when lighting pilot?

To light a pilot light, turn your home’s thermostat down or off. (Don’t skip this step!). Some directions tell you to turn the thermostat on and up to 75 or 80 degrees. If your thermostat is on and asking for heat, your main burners will ignite as soon as you light the pilot light.

Why does my furnace flame keeps going out?

Your furnace has a limit switch that keeps it from running if the heat exchanger is too hot. Dirty filters, closed or blocked vents and other blockages in airflow are common causes of an overheated furnace. A bad limit switch. The limit switch may be bad and need to be replaced.

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

$150 to $250





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.

How do I know if my thermocouple is bad on my furnace?

A bad thermocouple itself can prevent a gas furnace or boiler from working – if you can light the flame at the pilot manually but then the flame goes out when you release the manual gas feed valve, the thermocouple is probably bad.

What are the symptoms of a dirty flame sensor?

6 Signs of a Malfunctioning Gas Furnace Flame Sensor

  • Yellow Burner Flames. Open up or glance through the peephole of your gas furnace to see the color of the flames firing up in the burner. …
  • Rusted Flue Lines. …
  • High Utility Bills. …
  • Water Leaks. …
  • Old Age. …
  • Constant Thermostat Adjustments.


How do I find the thermocouple on my furnace?



Your furnace’s thermocouple is usually located right in the flame of the furnace’s pilot light. Its copper tubing makes it easy to spot. The thermocouple is made up of a tube, a bracket, and wires.

Can I replace a thermocouple myself?

It’s easy to replace and a new one costs $5 to $10. Rather than trying to unfasten the thermocouple inside the water heater’s burning chamber, it’s easier to remove the whole burner and thermocouple assembly.

Can you clean a thermocouple on a furnace?

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Why won’t my furnace flame stay on?



Probably the most common issue when dealing with a furnace that will not stay lit or ignite consistently is a dirty flame sensor. The flame sensor acts as a communication vehicle with the circuit board and tells it when a flame is lit inside the furnace.

How do you fix a flame rollout on a furnace?

Quote from the video:
Quote from Youtube video: You have to jumper out the pressure switch to what I'm imitating here is a failure of the heat exchanger that could cause that to happen and still keep the pressure switch closed it isn't real common.

How do you clean the flame sensor on a furnace?

Quote from the video:
Quote from Youtube video: As far as cleaning the sensor itself. There the factory recommended way of cleaning them is either with a piece of steel wool or actually scraping them with a straight edged knife.

Why does my furnace only run for a few minutes?

If your furnace shuts down after a few minutes, it’s likely due to a faulty or unhygienic flame sensor. This crucial component intends to monitor the gas burner. Also, when a flame sensor cannot detect the burner, the furnace runs for a few moments before shutting down and restarting.

Can thermostat cause furnace to short cycle?



A faulty thermostat can be a possible culprit for short cycling. If you’re experiencing a furnace short cycling, the first and easy thing you can do is check your thermostat to see if it’s performing correctly. Many times, a homeowner may forget to switch their thermostat over to the heating mode.

How do you know a thermostat is bad?

7 Ways to Tell Your Thermostat Is Broken

  1. Thermostat Has No Power. …
  2. AC or Furnace Won’t Turn On. …
  3. Heater or AC Won’t Turn Off. …
  4. Thermostat Doesn’t Match Room Temperature. …
  5. Thermostat Doesn’t Respond. …
  6. Short Cycling. …
  7. Thermostat Forgets Programmed Settings. …
  8. Thermostat Replacement Services.


Why does my furnace run for 5 minutes then shut off?

If your furnace turns off after a few minutes, there is a good chance it is caused by a faulty or dirty flame sensor. This vital component is designed to keep an eye on the gas burner. When it cannot sense that burner, the furnace runs then shuts off and starts again. This could be a relatively easy fix.

Why is my furnace shutting off after 15 minutes?



If your air filter is too dirty, it will restrict airflow. Your furnace will then shut off prematurely to avoid overheating. We recommend replacing flat filters once a month, and pleated filters every three months. It’s easy to stay on top of changing your filter by adding a Filter Reminder on your thermostat.