How to Troubleshoot a Coleman Gas Furnace With Green Blinking Lights


Coleman gas furnaces feature self-diagnostic tools to facilitate troubleshooting. An amber or red flash indicates a specific condition. Flashing green lights indicate that the diagnostic program did not find a problem with the furnace; however, your furnace may still not operate at its peak. If you believe your furnace isn't working properly despite the green lights, check a few common trouble areas. These include the settings, the blower door and the air filter, which may become clogged.

  • Check the settings on the furnace if it isn't functioning properly. If necessary, turn the electrical power and the manual gas shut-off valve on. Turn the switch on the gas valve to the “on” position.

  • Examine the furnace blower door. Ensure that it is fitted tightly into place. The blower door will automatically shut off power to the furnace if it isn't firmly in place.

  • Examine all components of the furnace, including the exterior, for signs of damage or deterioration. Call a professional technician if any part of the furnace appears damaged.

  • Check the chimney, vent connectors and heat exchanger for any obstructions.

  • Examine the drain lines for any possible cracks.

  • Look in the combustion air and vent pipe. Have a professional technician clean the pipe if it appears blocked or damaged.

  • Remove the filter for cleaning. Depending on your model, the filter is located in the return air duct or on a rack outside the main furnace casing. Hold the dirty filter under running water to remove all of the dust and grime. Wait for it to completely dry before replacing it. If you have a throwaway filter that is dirty, you'll need to replace it.

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