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65

6 red flashes, 5 green flashes — Heat-sink temperature sensor fault

Lennox · Communicating Systems

What does 65 mean?

The sensor monitoring the inverter's heat sink temperature is not working correctly. It's reporting temperatures outside the normal operating range. The outdoor unit will stop the compressor and fan.

Common Causes

  • Heat sink temperature sensor fault
  • Sensor reading too low or too high

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Moderate conditions may clear automatically. For critical conditions, disconnect power to the outdoor unit and restart.

  2. 2

    Ensure the outdoor unit is installed in an area with adequate ventilation.

Browse all codes in this manual (41)
Verified technical data. Last updated: April 2026

Related Faults

14Inverter Flash Code 14 (Red 1 flash, Green 4 flashes) — OD Inverter Compressor Slowdown21Inverter Flash Code 21 (Red 2 flashes, Green 1 flash) — OD Inverter DC Peak Fault262 red flashes, 6 green flashes — Compressor startup fail
Source: Lennox Communicating Systems
Open Manual (Page 64)Search more codes in this manual