Here’s what you need to know if your Lennox furnace is on the fritz.
What does a blinking light on a Lennox furnace mean?
Like Trane and Amana, Lennox furnaces are equipped with LED lights that are used to communicate issues. However, unlike Trane and Amana furnaces, Lennox HVAC systems use red and green lights to convey error codes. These lights flash in specific patterns to signify a particular issue.
If the red and green lights on your Lennox furnace are blinking simultaneously (quickly or slowly), this means that the furnace is functioning normally. All other patterns signify an issue that may require furnace repair.
How do you read Lennox error codes?
Lennox error codes are read based on the colour of the light that is flashing and how fast the light is blinking.
Here are some common error code patterns that you might see, along with details about what they mean.
| Lennox Furnace Error Codes | Meaning | Potential Issue |
| Red light – flashing quickly Green light – flashing slowly | Reversed polarity | Issue with electrical wiring |
| Red light – flashing slowly Green light – flashing quickly | Low flame error | Issue with flame sense rod, dirty flame sensor, poor gas pressure, etc. |
| Red light – flashing slowly Green light – solid | High limit switch open | Plugged filter, dirty blower wheel, ductwork issue, etc. |
| Red light – off Green light – flashing slowly | Draft inducer or pressure switch failure | Blocked inlet or exhaust vent, cracked hose, draft inducer not working, short in power switch, etc. |
| Red light – on, on, off Green light – on, off, on | Circuit board failure | Issue with control panel or wiring |
| Red and green lights alternating, flashing slowly | Flame failure | Issue with pilot light or ignition sensor |
| Red and green lights alternating, flashing quickly | Issue with voltage | Improper main ground |
