Lennox Error Code E106 indicates Twin communication fault. Start by checking the most common and safe items identified in the troubleshooting section. If the code returns after those checks, professional diagnosis is recommended.
Easy
Twin communication fault
Unknown
Power removed from one furnace and not the other or 24‑VAC supplies not in phase
Ensure both furnaces have power and that 24‑VAC supplies are in phase
Twin communication circuit
Call an HVAC technician if the error persists after completing the recommended basic troubleshooting steps or if the system repeatedly locks out.
Disconnect power before inspecting the equipment. Never bypass safety devices or operate the system if you suspect unsafe conditions.
Learn more about the furnace components and operating conditions commonly associated with diagnostic error codes: