Alert Code 434 — Communication error to main control

What does 434 mean?

Communication between the outdoor control and the inverter has been lost. The compressor will stop, and the indoor blower will not run. A critical condition occurs if this happens repeatedly.

• Loss of communication between outdoor control and inverter
• Incorrect power cycling during maintenance
• Loose wiring or connections

Click steps to track your progress.

1. 1

   Inspect all electrical connections for looseness or disconnections.

2. 2

   Make sure power to the outdoor unit is not interrupted while the indoor unit is powered, and vice-versa.

3. 3

   To clear a critical lockout: cycle power off and on for the outdoor unit, then cycle power off and on for the indoor unit (24VAC to the Lennox outdoor control).