Thermostat backlight is very dim or flickers, but the display content is still visible.

Safety first: Turn off HVAC power at the breaker before removing the thermostat from the wall plate.

• Step 1 – Check brightness settings: In the thermostat display settings, ensure brightness is not set to a low or eco mode.
• Step 2 – Inspect connectors: With the thermostat removed, gently press on the display module to ensure its connector is seated firmly on the main PCB.
• Step 3 – Measure supply voltage: Confirm that 24 VAC between R and C is stable; low voltage can cause dimming.
• Step 4 – Replace thermostat: If settings and voltage are correct but the backlight remains dim or flickers, the LED driver or LEDs are failing. Replace the thermostat head unit.