Thermostat powers on but screen is very dim or unreadable

Safety first: Isolate power before removing the thermostat.

Steps:

• Check the thermostat settings menu for brightness or contrast options and increase to a suitable level.
• Verify supply voltage at the thermostat terminals; low voltage can cause dim displays.
• Inspect for signs of moisture or condensation inside the display area.
• If settings and supply are correct but the display remains dim, the LCD or backlight driver has likely failed; replace the thermostat.