Replacement of navigation buttons on Xiaomi Mi 9C: from disassembly to assembly

Why do the buttons on the Xiaomi Mi 9C stop working?

Navigation buttons on Xiaomi Mi 9C (also known as Mi CC9 in some regions) are the underscreen touchpad that handles Back, Home and Recent Apps. Over time, users face typical problems: buttons stop responding to touch, fire spontaneously or work repeatedly. Causes of failure range from mechanical damage (falls, bumps) to wear of the plume or oxidation of contacts.

Unlike the physical buttons on older smartphones, the touchpad on the Mi 9C is integrated into the display module, but connects through a separate flexible plume. This means that replacing the buttons does not always require a complete change of the screen – often just change the navigation bar plume or clear the contacts. In this article, we will discuss three main repair scenarios: cleaning contacts, replacing the plume and completely replacing the display module (in extreme cases).

Before you start repairing, it's important to diagnose the problem: If the buttons don't work after the phone falls, most likely the plume is damaged or the contacts have gone away. If the malfunction has gradually manifested itself (the buttons first stuck and then stopped responding), wear or oxidation is to blame. In rare cases, the software is to blame - but this is easy to check by connecting the phone to a computer and testing the sensor through ADB.

Diagnosis of malfunction: how to understand what exactly broke

Before disassembling the phone, you need to make sure that the problem is in the hardware, and here are four steps to diagnose:

• 🔍 Software Failure Check: Reboot your phone in Safe Mode (hold the power button) → long tap on "Switch off" → "Restart in Safe Mode. If the buttons are triggered, the third-party app is to blame.
• 📱 Sensor Test: Use apps like the Touch Screen Test (available on Google Play) to check the response of each button.
• 🔌 Contact check: Connect your phone to charge and press the bottom of the case slightly. If the buttons start working, it's the fault of the departed plume.
• 💻 ADB-Test: Connect Mi 9C PC, turn on Debugging on USB And then you run the command: adb shell getevent. -l Touching buttons should be displayed in the log. If not, the problem is in the plume or module.

If all the tests confirm a hardware malfunction, move on to disassembly, but first prepare tools and parts.

Preparation for repairs: tools and spare parts

To replace the navigation buttons on the Xiaomi Mi 9C, you will need:

Important: When buying a plume, check for compatibility with the Mi 9C model (device code - pyxis). Some sellers indicate compatibility with the Mi CC9 or Mi 9 Lite, but these models have different plumes! Also check that the package includes two insulator stickers for attaching the plume to the case.

⚠️ Warning: If you've never disassembled smartphones, practice on an old device. - Navigation panel plumes in Mi 9C extremely fragile - they are easy to break with careless handling.

Backup data | Charge your phone at least 50% | Prepare your workplace (clean surface, good lighting) | Turn off your phone before disassembly | Check for all tools-->

Step-by-step: disassembly of Xiaomi Mi 9C and replacement of the plume

The process of replacing the navigation buttons involves completely disassembling the phone.

1. Removal of the back cover: 🔥 Heat the edge of the back cover with a hair dryer (or thermo-air station) for 2-3 minutes. 🪛 Insert a plastic blade into the gap between the body and the lid (start at the lower right corner). Carefully drive the blade around the perimeter, separating the lid. ⚠️ Do not make excessive efforts - under the lid are the plumes of the fingerprint scanner and antennas.
2. Battery shutdown: 🔋 Unscrew 5 screws fixing the metal plate of the battery. 🧲 Put a battery plume in a plastic blade and disconnect it from the motherboard. Never disassemble a phone with a battery connected, which can cause a short circuit!
3. Dismantling of motherboard: 🔧 Unscrew all the screws (about 15) and gently raise the board. It is attached to several plumes: cameras, display, power buttons / volume. 📱 The navigation bar plume is located under a metal screen next to the charging connector.

Replacement of the plume:

• 🆕 Install a new plume in the connector on the motherboard. It should click without effort.
• 🧴 Put a drop of glue on. B-7000 to the place of attachment of the plume to the body and press.

After the plume is replaced, put the phone back together.

• 🔌 Connecting the battery plume (must be tightly inserted).
• 📶 Proper stacking of antenna plumes (they are easily crumpled).
• 🔒 Swirling all screws - a missed screw can cause a board skew.

Cleaning contacts: alternative to replacing the plume

If the buttons on the Xiaomi Mi 9C are unstable (they react, then they don’t), the problem may be oxidation of the contacts on the plume or the motherboard connector, in which case cleaning will help:

1. Remove the navigation bar plume from the connector (as described in the previous section).
2. Process contacts: 🧴 Apply the isopropyl alcohol on a cotton swab. 🔄 Carefully wipe the contacts on the plume and motherboard connector. 🌬️ Let it dry for 5-10 minutes (do not use a hair dryer!).

Check the plume fixation: sometimes the contacts oxidize due to the bad fit. Add a thin strip of insulation tape under the plume for better pressing.

If you've had the buttons work after cleaning, but the problem comes back after a few days, the plume is worn out and needs to be replaced, and oxidation is just a symptom, not a cause.

⚠️ Warning: Do not use acetone, vodka or other aggressive liquids to clean! They can damage the plastic elements of the plume. Only isopropyl alcohol (90% and above).

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If you don't have isopropyl alcohol on hand, you can use an eraser to clean the contacts. Carefully wipe the contacts on the plume with a stripe, this will remove the oxides without the liquid.

Replacement of the display module: when necessary

In rare cases, the navigation buttons on the Mi 9C stop working due to damage to the touch layer of the display, this happens when the phone is hit hard or has been in water, in which case the entire display module needs to be replaced.

• 📱 The buttons don’t work, but the rest of the touch screen is functioning normally.
• 💧 On the screen, you can see stains or stains under the glass (infection of moisture).
• 🔧 After replacing the plume, the buttons still do not respond.

The process of replacing the display with the Mi 9C is more complicated than replacing the plume.

1. 🔥 Heat the screen around the perimeter with a hairdryer (temperature 60–70)°C).
2. 🧲 Push the screen with a suction cup and carefully separate it from the body, starting at the bottom edge.
3. ⚠️ Be careful - under the screen pass the plumes of the sensor and display.
4. 🆕 Install a new display module, connect all the plumes and assemble the phone.

The cost of the original display for the Mi 9C is ~ 3000-5 000 rubles (2026), while the plume of the navigation panel will cost 500-1 000 rubles. If you are not sure about the cause of the breakdown, start with a replacement plume – it is cheaper and easier.

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Replacing the display module is only justified if the screen is damaged mechanically or moisture is ingested, and 80% of the time the problem is solved by replacing the plume or cleaning the contacts.

Software solutions: if the buttons do not work because of the software

In 5 to 10% of cases, the navigation buttons on the Xiaomi Mi 9C stop working due to software failures.

• 🔄 Reset sensor settings: Go to Settings → System system → Additionally. → Resetting sensor settings.
• 📱 Disable gestures: If you use gestures instead of buttons, try returning standard navigation to Settings → Display. → Navigation panel.
• 🐞 Firmware Update: Check for updates in Settings → The phone. → Updating the system.
• 🔧 ADB-commands: If the buttons don’t work only in some applications, do: adb shell pm clear com.android.systemui This will reset the system interface cache.

If the software methods did not help, and the diagnosis showed a hardware malfunction - proceed to disassembly.

Frequent Mistakes When Replacing Buttons with Xiaomi Mi 9C and How to Avoid Them

Even experienced craftsmen sometimes make mistakes when repairing the Mi 9C. Here are the most common:

Another common mistake is to mix the plumes when you build them. On the Mi 9C, the navigation bar plume looks like a fingerprint scanner plume, but it has a different wiring. Always check the marking before you plug in!

FAQ: Answers to Frequent Questions