E17 displayed and thermostat indicates internal over‑temperature; device may shut down or dim the display.

Safety: Turn off power to the HVAC system before removing the thermostat from the wall.

• Step 1 – Check environment: Ensure the thermostat is not installed above a heat register, near a fireplace, or in direct sunlight. If it is, plan to relocate it to an interior wall.
• Step 2 – Inspect wall cavity: Remove the thermostat and feel inside the wall opening for excessive heat from hot water pipes or ductwork. If present, add insulation behind the thermostat or relocate it.
• Step 3 – Clear vents: Make sure the thermostat’s side and bottom ventilation slots are not blocked by paint, dirt, or wall plates. Gently clean as needed.
• Step 4 – Reduce load: If multiple accessories are powered through the thermostat, consider powering them from a separate transformer to reduce internal heating.
• Step 5 – Replace thermostat: If E17 occurs in a normal environment, the internal power regulator or sensor may be failing. Replace the thermostat.