Thermostat displays a warning that auxiliary heat is running excessively or not responding

Safety: Auxiliary heat often involves high-current electric elements. Turn off power to the air handler at the breaker before working on wiring.

• Step 1 – Check ecobee AUX configuration: Go to Installation Settings > Equipment and verify AUX is assigned correctly (electric heat vs. gas, number of stages, lockout temperatures).
• Step 2 – Inspect AUX wiring: At the thermostat, confirm the AUX wire is in the AUX/W2 terminal. At the air handler or furnace, confirm it is on the correct W2/AUX terminal.
• Step 3 – Observe AUX runtime: In the ecobee app or on the thermostat, review runtime reports. If AUX runs constantly, lower the AUX temperature threshold or increase compressor minimum runtime.
• Step 4 – Test AUX relay/sequencer: With a heat call for AUX, check for 24 VAC at the AUX terminal on the control board. If present but the elements do not heat, the relay or sequencer may be faulty and should be replaced by a technician.