Code 35 — Furnace Modulating Gas Valve Communications Fault

What does 35 mean?

This fault indicates a communication problem with the furnace's modulating gas valve. The control system is unable to send commands or receive feedback from the gas valve, affecting heating control.

• Loose or damaged wiring to the gas valve
• Faulty modulating gas valve
• Control board communication issue
• Power fluctuation to the furnace

Click steps to track your progress.

1. 1

   Turn off the power to the furnace at the circuit breaker for at least 30 seconds.

2. 2

   Restore power and observe if the furnace attempts to operate.

3. 3

   Ensure there are no error messages on the thermostat display.

4. 4

   If the communication fault persists, contact a qualified HVAC technician, as this involves the gas system.