How to Troubleshoot a Slow Flash on a Lennox Elite Furnace

The Lennox Elite furnace has a control box on the front of the furnace where the circuit breaker, ignition and display panel are located. When issues occur with the Lennox furnace, an indicator light will flash slowly or quickly in a pattern to notify users of the problem. If the error light is blinking slowly, troubleshooting efforts are required to return the furnace to normal performance.

Step 1

Watch the flashing lights to determine their color and speed. Red and green lights flashing simultaneously in a slow pattern indicate normal operation. No further action is needed.

Step 2

Turn the thermostat up higher if the light continues to flash and the furnace is not turning on or emitting heat. The light indicates that there is power but no call for heat.

Step 3

Disconnect power to the Lennox furnace if the lights keep blinking, particularly if the light is red. Open the access panel when the furnace is cool and clean the flame sensor with a clean, dry cloth.

Step 4

Remove the air filter while the power is still disconnected and clean with a vacuum cleaner attachment. Vacuum the interior of the furnace as well, including the fan. Place the filter back into the furnace. Restore the access panel and power, ensuring that the gas valve supply is turned on.