Gas Valve & Gas Supply Issues The pilot light depends on a reliable source of gas or propane in order to stay lit. Any issues with the gas valve that supplies that gas to the flame, whether it be dirty or malfunctioning, can result in that flame going out.
The issue could be: A dirty tube: If the pilot light tube is dirty, it can put out the light over time. You'll need to clean it with something abrasive to get it working again. Not enough gas: Sometimes, the gas valve will leak, or something else prevents gas from getting through the line.
The Fix: Pilot Light to Gas Fireplace Won't Stay Lit
This can be an indication that your fireplace thermocouple is either bad or worn out. However, if your pilot is lit but the gas fireplace isn't, then there's probably a problem with your thermopile.
A working thermocouple will give a reading of between 25 and 30 millimeters. If the reading is less than 25 millimeters, it should be replaced.
The Pilot Lights But Won't Stay Lit
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.
For those who prefer not to attempt a DIY repair, hiring an HVAC technician is a safer option. The cost for a professional furnace thermocouple replacement usually ranges from $80 to $150, depending on your location and the specific HVAC company. This price includes both the part and labor.
Thermocouple Malfunction
It is positioned very close to the flame, and when lit, the pilot light tells the thermocouple to keep the gas line open. A thermocouple that is dirty or malfunctioning will often shut off your gas supply in error, causing the pilot light to go out and your furnace to stop working.
There are two main reasons why your thermocouple might fail. The first is age. For the most part, your thermocouple is more likely to fail once it takes on some wear and tear. Additionally, thermocouples can sometimes fail due to manufacturer defects.
To figure out if your thermocouple is dirty, look at its tip. If you notice the tip is covered with a layer of soot, this means it needs to be cleaned as soon as possible. If you ignore this, you'll start having problems with the pilot light staying lit on a consistent basis.
Is It Dangerous if The Pilot Light Goes Out? 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.
It shouldn't be able to re-light itself. It should have a bi-metal strip which prevents gas being delivered unless the pilot has heated the strip to sustain it on. If the pilot goes out regularly then the pilot flame is either being blown out or the bi-metal strip is faulty.
Take a soft brush such as an old toothbrush and gently remove any visible debris from the pilot orifice, flash tubes and ignitors. Next, insert a sewing needle or thin wire into the pilot orifice, the flash tubes and the holes in the ignitors, as well as in the burners, wiggling it gently to dislodge any debris.
Keep the gas control knob held down for a further minute until the flame starts turning blue. Once you have released the knob, the pilot light will usually continue to burn, however, if it goes out again, the re-ignition hasn't worked and you should repeat the steps.
Common reasons include a nearby draft, dirt buildup, or a malfunctioning thermocouple. Another pilot light drawback is energy waste. Since the pilot light needs to remain active, your furnace is always consuming some gas. It's not a lot—usually just a few therms of gas a month–but that obviously adds up over time.
Clean the thermocouple - using the emery cloth sandpaper, sand the ends of the thermocouple and then give it a finishing touch with the lint-free cloth. Hopefully, you can get to the ends of the thermocouple without having to detach it from the assembly, but you may have to do that.
Blockages in the Flue Pipe
Once the gas starts to build up, this may cause your heater to overheat and turn off early. If your furnace keeps shutting off after a couple of minutes, it may be necessary to work with a licensed professional to remove the blockages in your flue pipe and HVAC system.
Faulty Thermocouple – If the pilot light goes out, it's up to the thermocouple to cut the gas off.
A gas-powered heater uses a pilot light to ignite the flame that heats your home. The pilot light is a small, continuous blue or yellow flame that is ignited by a spark from an igniter or thermocouple. When this flame goes out, it can cause the gas to leak from the burner and into your home.
You can reset the ignition on your furnace simply. To do this you must cut the power to the furnace first by turning off the circuit that powers it. Once the power is off you can remove the burner door to reveal the ignitor. Turn this to “off” and leave it off for at least 5 minutes.
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.
A heat exchanger replacement is often one of the most costly repairs in a furnace, and the expense can sometimes rival that of installing a new furnace. Typical replacement costs vary widely but can easily reach several thousand dollars, especially if labor costs are factored in.
Once you have replaced the thermocouple, turn on the furnace and check to see if the pilot light stays lit. If your pilot light doesn't stay lit, it may be due to something blocking the thermocouple. You can try cleaning or replacing it, but if that doesn't work, you may need to call a professional.