MX Keys adaptive backlight is driven by an ambient light sensor. Three possible causes if LEDs no longer light: the sensor is blocked (dust, sticker), a Logi Options+ setting is misconfigured, or the LEDs have died (rare, but possible after 5+ years of heavy use).
Diagnostic
Quick test: open Logi Options+ → MX Keys → Backlight → set to 100% manually. If LEDs come on, it was a sensor question (cover the keyboard with your hand to simulate low light — LEDs should react). If nothing lights even at manual 100%, it's hardware: LEDs or motherboard LED controller.
Méthode
- 1
Check in Logi Options+ that backlight is not disabled.
- 2
Clean the light sensor above F5/F6 with a dry cotton swab.
- 3
Force 100% manually in Options+ to test.
- 4
If still nothing, motherboard LED controller likely faulty — €15 for the part.
FAQ
Why does MX Keys backlight consume so much?
The 10 individual LEDs consume about 10× the idle power. Logitech rates 10 days battery with backlight on vs 5 months off. Disable if you want to save battery.
Can a broken MX Keys LED be replaced?
Theoretically yes, but LEDs are SMD soldered on the motherboard — microscopic operation. In practice, replacing the motherboard (€15) is simpler and cheaper.
Does the backlight make my keyboard 'gaming'?
No, MX Keys LEDs are white and adaptive (light up when hand approaches). No RGB, no 'gaming' modes. It's designed for office work.
In 80% of cases, MX Keys backlight not working = Logi Options+ setting. 5 seconds of check before suspecting hardware.