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36

Alert 36 — Heating when Not Requested

Lennox · Communicating Systems

What does 36 mean?

The system has been heating for at least 15 minutes without a demand for heating. This is displayed on the thermostat's HD display.

Common Causes

  • Unexpected demand for heating.
  • Other alert codes preventing normal operation.
  • Issue with heating equipment.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Run the system in diagnostic mode to verify operation.

  2. 2

    Check for other alert codes that might be causing this issue.

  3. 3

    Inspect all heating equipment to find the cause of the heating demand.

  4. 4

    Recycle power to the system.

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 29)Search more codes in this manual