A gas or oil furnace depends upon the pilot light to ignite the fuel so that the appliance can provide heat. If your pilot light malfunctions, you can be left in the cold. The following are some of the issues that could be affecting the pilot light on your furnace.
The pilot light valve is the opening where the gas and the light emerge from. Dust and dirt can collect around the valve opening, resulting in issues with the pilot light. The light may go out easily or burn a color other than blue or white due to the foreign materials in the valve. In some cases, the valve may even be blocked, which makes it impossible to light the pilot at all. Your furnace service technician can temporarily cut the gas and power to the furnace so that they can safely clean or replace the valve.
The fuel regulator controls how much fuel is being delivered to the furnace. If the regulator fails or malfunctions, insufficient fuel could be delivered. This will result in a light that fails to light, won't stay lit, or burns weakly. In some cases, too much fuel may be delivered, which can trip a safety switch and cut off the pilot light completely. Your tech has the ability to inspect the regulator to determine if it is the cause of the problem. If it is, you will need to have the regulator replaced.
The thermocouple is the pilot flame sensor in your furnace. This copper rod acts as a safety sensor. If the pilot flame isn't heating up the thermocouple, then it cuts off the gas to the furnace so that you don't have the potential of a dangerous gas leak. Thermocouples can fall out of alignment, or they can become dirty. In rare cases, they fail completely. A service tech will determine which cause is affecting your furnace so that they can either clean and realign the thermocouple, or replace it completely.
Sometimes pilot light issues are actually an environmental problem. Drafts that blow into the furnace can actually blow out the pilot light. Draft issues with the pilot light are more common in windy conditions, when a draft may blow through an output duct and into the furnace. Contact a service tech to inspect your furnace for any drafts. They can seal up the area to prevent future problems.
Contact a furnace repair contractor in your area for more help.