Thermostat backlight or display is very dim and hard to read

Safety: Turn off power before removing the thermostat from its base if you need to inspect wiring.

• Adjust brightness: In the display settings, increase brightness and contrast to maximum and check if readability improves.
• Check power source: Ensure the power adapter or boiler low-voltage supply is within specification.
• Ambient light sensor: Some models dim automatically in low light; test by shining a light on the sensor area to see if brightness increases.

If the display remains very dim, the backlight or driver is failing and the thermostat should be replaced.