What to Do When the Garage Furnace Pilot Light Flame Covers the Thermocouple Tip

What You'll Need
Wire brush

Occasionally, when it is time to light the pilot light on your garage furnace for the approaching winter season, you may run into a variety of problems. Sometimes the pilot light will not stay lit and sometimes it seems like although it stays lit, it makes a roaring sound. The steps below have been written to help homeowners troubleshoot and fix problems that might arise when the garage furnace pilot light flame covers the thermocouple tip.

Step 1 - Locating and Troubleshooting the Pilot Light

In order to find the pilot light in your furnace, you will need to remove the access panel which is usually located near the bottom of the furnace. To do this, slide the panel up and then yank it away from the furnace. Once inside your furnace, use your flashlight to locate your pilot light, which is usually located along the bottom of the furnace. Right beside the pilot light, you will find the thermocouple, which plays a significant role in whether your pilot light is performing well or not. Before making any adjustment to the pilot light on your garage’s gas furnace, take a good look at the flame, which should be burning with a blue flame that reaches a height of about ½ inch of the thermocouple. If the flame overlaps or covers the thermocouple tip, then the gas pressure feeding into the pilot light is set too high, and needs to be adjusted so that the pilot light is receiving less gas to burn.

Step 2 - Making the Adjustment to the Pilot Light Flame

In order to make the necessary adjustment to your pilot light, you will first need to locate your pilot light’s screw adjustment for the gas pressure. This is usually, on most furnaces, located at the end of the pilot light’s gas supply tube, which is where the gas supply tube connects to the gas. Making this adjustment usually requires the use of a flat head screwdriver. Using the flat head screwdriver, insert it into the slot and turn the screw counter-clockwise to enlarge the size of the flame, or clockwise to reduce the size of the flame. When making the adjustment, you are wise to do it in very small increments, and then test the pilot light’s burning flame between each adjustment, until you find the correct gas pressure to supply the pilot light with the correct flame size.

Step 3 - Testing the Pilot Light Adjustments

Between tests, be sure to turn the gas off. If the pilot light doesn’t burn clean, you may need to use your wire brush to remove any debris that is causing the tube to splutter or clog. Simply spin the brush gently around the tube being careful not to cause permanent scratches. After cleaning the tube and adjusting the gas flow, try relighting your pilot light and observe the flame.  If you have still too much gas pressure or not enough, shut the gas off again and adjust the pilot light screw again. Turn the gas back on and watch the flame. Continuing this procedure until the pilot light is burning blue and covers the thermocouple’s end by half an inch, but no more. A well functioning pilot light is essential to smooth furnace operation.