Thermostat displays H1, indicating a high temperature detected at the thermostat.

Safety: No high-voltage work is required. Do not open the thermostat casing.

• Step 1 – Verify actual room temperature: Use a separate thermometer placed near the thermostat but out of direct sunlight. Compare the readings.
• Step 2 – Check for heat sources: Look for lamps, TVs, routers, or other electronics directly below or behind the thermostat. Relocate these items if possible.
• Step 3 – Block direct sunlight: If sunlight hits the thermostat, add a shade or curtain, or consider relocating the thermostat to an interior wall.
• Step 4 – Seal wall cavity drafts: Remove the thermostat from the backplate and check for hot air leaking from the wall cavity (e.g., from uninsulated spaces). Seal gaps with low-expansion foam or putty, avoiding the backplate contacts.
• Step 5 – Replace thermostat if sensor is faulty: If the Ecobee consistently reads much higher than actual temperature with no environmental cause, the internal sensor may be defective and the thermostat should be replaced.