Why Xiaomi’s screen dims or spontaneously darkens – a full analysis of the reasons

Have you noticed that your Xiaomi smartphone screen has become dim, as if covered with gray film? Or brightness spontaneously changes without your participation, preventing comfortable use? This problem is found on models from the Redmi Note 10 Pro to the flagship Xiaomi 13 Ultra, and its causes can be hidden in both system settings and hardware malfunctions.

In this article, we'll look at all the possible causes of screen dimming, from the commonplace failure of the light sensor to the wear of the matrix or damage to the plume, how to diagnose the problem yourself, which settings to check first, and when to contact the service center, and pay special attention to the hidden features of MIUI, which can affect the brightness of the screen without your knowledge.

If your Xiaomi is getting worse at displaying colors, the backlight is flickering, or the screen goes out when you tilt it, don't rush to carry it for repair. In 70% of cases, the problem is solved software-based in 5 minutes. Let's start with the simplest.

1. Automatic brightness control (illumination sensor)

The most common cause of spontaneous dimming is the light sensor, which is responsible for automatic brightness control, and if the sensor is contaminated, damaged, or simply malfunctioning, the screen can dim even in good lighting.

To test this hypothesis:

• 🔍 Turn off automatic brightness in settings: go to Settings → Display. → Autobrightness and deactivate the slider.
• 📱 Check the cleanness of the sensor (usually located next to the front camera.
• 🔄 Reboot your phone – sometimes the sensor “hangs” after the update MIUI.

If you turn off the autobrightness, the screen stops dimming, the problem is the sensor.

• 🛠️ Contact the service for cleaning / replacing the sensor (cost) ~500–1500 ₽).
• 📲 Use brightness calibration applications (e.g. Lux Auto Brightness).
• 🔧 Manually adjust the brightness curve through the engineering menu (more in the section about hidden functions).

2 Hidden MIUI functions that affect brightness

Xiaomi is known for its MIUI firmware features, which are not always obvious to the user, some of which can force the screen to dim under certain conditions.

• 🌙 Read mode: Turns on automatically during dark hours or when you run certain apps (such as Kindle or Wattpad) → Display. → Reading mode.
• 👁️ Eye protection: The blue light filter can make the screen yellowish and dim. Set a schedule or turn off in Settings → Display. → Protection of vision.
• 🔋 Charge savings: In Ultra Battery Saver or Super Economy modes, the system limits brightness to 30-50%. → Battery → Savings regimes.

MIUI also has a hidden function called Adaptive Backlighting, which analyzes the contents of the screen and reduces the brightness when displaying dark images, and you can only turn it off via the engineering menu:

Turn off Reading Mode

Turn off vision protection.

Check battery saving modes

Reset the display settings to factory-->

#36446337## (to log into the engineering menu)


Go to Display → Adaptive Backlight → set the value to 0

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If the screen is dim after the MIUI update, try resetting the display settings: Settings → Display → Additional → Reset. This will return factory brightness and color reproduction.

3. Software failures and firmware errors

If the screen blackout started after the MIUI update or installing third-party apps, the problem may be a software failure.

• The screen dims at regular intervals (e.g., every 10 minutes).
• The brightness is reset after blocking/unlocking.
• In Settings → Battery → Use of abnormal energy consumption by system processes is visible.

What to do:

1. Clear the system cache: Go to Settings → Memory → Clean. Select “Clear App Cache” and “Clear System Cache”.
2. Remove problematic apps: Launch your phone in Safe Mode (hold off button → Safe Mode) If the safe mode screen is working normally, third-party software is to blame. Remove the last installed apps.
3. Reverse Update: If the issue has occurred after the MIUI update, try rolling back to the previous version via Settings → About Phone → System Update → Three Points → Select the Service Pack.

If the failures continue, you will have to reset the phone to the factory settings or reflash it through the Fastboot. Instructions for specific Xiaomi models can be found in our section on reset.

Hardware malfunctions: matrix, plume, backlight controller

If the software methods didn't work, it's probably hardware, and here are the most common malfunctions and their signs:

How to diagnose a hardware problem:

• 🔦 Light a flashlight on the screen at an angle - if the image is clearly visible, but the backlight is weak, to blame LED-lighting.
• 📱 Check the reaction to pressing: if the pressure on certain areas the screen becomes brighter, the problem is in the plume.
• 🌡️ Heat your phone (for example, leaving it in the sun) – if the dimming gets worse, a controller malfunction is possible.

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If the screen dims when the phone is tilted, 90% of the time it is the fault of the broken or broken plume, a problem that is common in curved screen models (Xiaomi Mi 11 Ultra, Redmi K50 Pro).

⚠️ Attention! Don't try to disassemble your phone to check the plume unless you're experienced, and damage to the flexible cable will cause you to lose your image completely and cost you more to replace.

5.CPU overheating and trottling

Many Xiaomi users experience screen dimming due to overheating of the processor, and when the chipset temperature exceeds 60-70°C, the system is forced to reduce the brightness and performance (thermal throttling), which is protection against damage to components.

How to check:

• 📊 Install a temperature monitoring app (for example, CPU Monitor AIDA64).
• 🔥 Run a resource-intensive application (game, benchmark) and watch the temperature.
• 📉 If the screen dims when heated, and after cooling, normal brightness returns - the problem is overheating.

Decisions:

• 🧊 Clean your phone from dust (especially important for models with a removable back cover, such as the Redmi Note 9 Pro).
• 🔋 Replace the heat paste on the processor (in service, cost) ~1 000–2 000 ₽).
• 📵 Avoid using your phone in the sun or near heat sources.
• 🔄 Turn off background processes in Settings → Battery → Optimization.

On some models (POCO F3, Xiaomi 12T) overheating is caused by a defect in the cooling system, in which case only replacing the heat pipes in the service will help.

6. Battery wear and power problems

Few people know, but a worn-out battery can affect the brightness of the screen. When the battery degrades, it can't provide enough current to backlight, and the system forces the brightness to decline.

• The screen dims at a charge level below 20-30%.
• The phone turns off at 10-15% charge.
• In Settings → Battery → The state is shown more than 500 charging cycles.

How to check the battery:

1. Install the AccuBattery app and check the actual battery capacity.
2. If the capacity has fallen below 70% of the factory, the battery needs to be replaced.
3. Check the battery voltage in the engineering menu (#4636## → “Battery Information”). Normal: 3.7-4.2V.

Decisions:

• 🔋 Replace the battery (cost for popular models: Redmi Note 10 – 1,200) ₽, Xiaomi 11T — 2 500 ₽).
• 🔌 Use the original charger (low-quality RAMs can cause voltage drawdowns).
• 📵 Turn off fast charging in Settings → Battery → Fast charging if the phone overheats.

⚠️ Attention! On Xiaomi models with wireless charging support (Mi 11, 12 Pro), the screen dimming when charging can be caused by a Qi coil malfunction.

7 Factory dumping and reflashing as last resorts

If all the previous methods failed, there are two radical solutions: factory reset or firmware, which should only be used in case of software failures, since they erase all data.

Factory reset (Hard Reset):

1. Make a backup of the data through Settings → About Phone → Backup.
2. Go to Settings → Additional → Recovery and Reset → Resetting.
3. Select “Erase all data” and confirm.

Fastboot Flashing (for experienced users):

1. Download the official firmware for your model from the Xiaomi Firmware website.
2. Install the Mi Flash Tool on your PC.
3. Transfer the phone to Fastboot mode (hold Power + Volume down).
4. Connect to your PC and run through Mi Flash (select Clean All option).

After flashing, check the brightness of the screen in test mode (##6484## → “Manual Test” → “Display”). If the problem persists, it is a hardware malfunction.

FAQ: Frequent questions about Xiaomi screen dimming