7 Possible Reasons the Pilot Light on Your Gas Furnace Won’t Stay Lit

October 10, 2022
Furnace maintenance in Roseville, MI

Many furnaces still rely on a pilot light to combust natural gas and create heat. When the pilot light goes out for any reason, you won’t have heat until you relight it. This problem is usually easy to spot as your HVAC system will start blowing cold air. If the pilot ever goes out, it is usually easy to relight it. If you can’t get your pilot to stay lit or if it doesn’t light at all, then you’re most likely dealing with one of the issues below.

1. The Thermocouple Is Dirty or Bent

Many pilot light issues are related to the thermocouple. This is a thin metal probe that detects when the pilot is lit and controls the gas flow to the furnace. When the pilot is lit, the flame heats up the thermocouple. Once heated, the thermocouple signals the gas valve to open whenever the furnace needs to run.

The thermocouple also controls the gas to the pilot light. When you first light the pilot, gas only flows when you press the reset button. As soon as you release the button, the gas will stop flowing if the thermocouple isn’t adequately heated. This is why you always need to hold the reset button in for around 30 seconds, as this allows the pilot flame to heat the thermocouple. The flame will go out if you release the knob before it is hot.

The thermocouple can become dirty and caked with grit, preventing it from heating up and detecting that the pilot is lit. As a result, the pilot will always go out after you release the reset button. You can solve this problem by gently cleaning the thermocouple probe with fine sandpaper and then wiping it off with a soft cloth. However, be careful not to bend or damage the probe. A damaged thermocouple will need to be replaced by an HVAC technician.

This same issue can also occur because the thermocouple is bent and not close enough for the flame to heat it. To check this, light the pilot and make sure that the probe is close enough that it is completely engulfed in flame. If it looks bent or doesn’t touch the flame, try to gently bend it back in place and see if the pilot will now light.

2. The Pilot Tube Is Clogged

Another common reason that a pilot light won’t stay lit is because of a clogged pilot tube. Gas travels through the pilot tube to keep the pilot light burning. If the tube is completely clogged, no gas will flow, and you won’t get the pilot to ignite at all. A partially clogged tube can cause the flame to be weak and yellow.

This issue can be fixed by cleaning the tube out with a needle or paperclip and then trying to see if the pilot will stay lit. When looking at the pilot light, you’ll see a thin metal tube near where the flame should be. Gently working a needle in the hole should clear out any dust or debris so gas can flow properly.

3. Thermocouple Is Worn Out

Thermocouples can also wear out and stop working altogether. The thermocouple needs to have a small electrical current flowing through it for your furnace to work properly. An electric signal tells the gas valve when it should open. When the thermocouple wears out, there won’t be any current, and therefore, the valve will stay closed. The thermocouple can also become loose, and this will also prevent electricity from flowing to it properly.

An HVAC technician can test for this problem by using a multimeter. If the readings aren’t normal, the thermocouple is loose or broken. If it is broken, then it will obviously need to be replaced. If the technician finds that the thermocouple is clean, in the proper position, and has an electrical current, they will inspect your furnace for other issues that may be causing the pilot light to go out.

4. Exhaust Vent Has an Air Leak

Furnace pilot lights can sometimes get blown out due to wind gusts or drafts. If you find that your pilot goes out often, it could be that there is a leak in the outlet duct where the hot air flows out of the furnace. When this happens, it can allow enough air to escape to blow the pilot light out. This problem can be fixed by having an HVAC technician reseal the ductwork.

The same issue can also happen if there are leaks or gaps around the exhaust pipe or flue. This problem is potentially more serious as the flue works to vent carbon monoxide to the outside of your home. If the flue isn’t working properly, it could lead to this dangerous gas filling your home. If you notice any drafts around the exhaust vent, you should immediately contact a certified HVAC professional and leave your furnace off until it has been inspected.

5. Pilot Control Is Faulty

If you can’t get your pilot light to ignite at all, it could be that the pilot control is no longer working properly. This problem is fairly rare, but it can happen in older furnaces. The good news is that the control panel can be replaced. While the process is a bit more involved than replacing the thermocouple, it is still better than needing to have a new furnace installed.

6. Gas Regulator Is Malfunctioning

The gas regulator is located at the meter outside your home and controls the flow of natural gas coming into the building. The regulator can sometimes malfunction due to damage or simply because of age. This won’t just affect your furnace but also every other gas appliance in the home. In this situation, you will need to contact your gas company to have the regulator inspected and replaced.

7. Gas Supply Issues

Pilot light issues can also be caused by problems with the local gas supply. Sometimes demand outweighs the available supply and can cause the gas to flow at reduced pressure or occasionally go out entirely. This problem will affect all of your gas fixtures. It will also usually result in your neighbors experiencing the same issue. Unfortunately, there is nothing you can do about this type of gas supply issue.

Metro Detroit’s Residential Heating Experts

If you’re having issues with your furnace’s pilot light or any other trouble with your heating system, you can count on C & C Heating & Air Conditioning to get the problem solved quickly. Our certified HVAC technicians have years of experience and the knowledge to quickly fix furnace problems. Should your furnace need to be replaced, we can help you understand your options and choose the best model for your home and budget.

We carry furnaces and air conditioners from top brands like Lennox, Trane, and Carrier. We also install a range of other products, including water heaters, ductless mini-splits, whole-home humidifiers and dehumidifiers, and air filtration systems. If you need help with your pilot light or any other HVAC service, give C & C Heating & Air Conditioning a call today.

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