Summary of Common Mobile Phone Fault Repair Methods

As a mobile phone repair shop owner, I encounter various mobile phone faults in my daily work, many of which are frequent and typical. To improve repair efficiency, ensure repair quality, and facilitate subsequent employee training and customer consultation, I have summarized common mobile phone faults and corresponding repair methods below, covering core modules such as screen, battery, charging, sound, and system.

I. Screen Faults: Core Issues of Vision and Touch

The screen is the main medium for interaction between the mobile phone and the user. Faults manifest in various ways, requiring differentiation between hardware damage and software issues for accurate diagnosis and repair.

(1) Common Symptoms and Causes

- Black Screen/White Screen/Distorted Screen: Core causes include loose or oxidized screen cables (often caused by drops or pressure), damaged screen assembly (severe drops or water damage), motherboard display chip failure (caused by high temperature or unstable current), and software crashes (system crashes or malware).

- Touchscreen Malfunction: Mainly caused by poor contact in the touchscreen cable, damaged touch layer (drops or heavy object impact), oil/water stains interfering with the screen surface, and abnormal system touch calibration.

- Screen Crack: This is divided into outer screen (cover glass) cracks and inner screen (display + touch layer) cracks. Almost all are caused by external impact. Outer screen cracks usually do not affect display and touch, while inner screen cracks are often accompanied by black screen, distorted screen, or touch malfunction.

(2) Repair Methods

- Black Screen/White Screen/Distorted Screen Troubleshooting: First, force restart the phone (the operation varies depending on the brand; for Apple, press and hold the power + volume buttons, while for Android it's usually pressing and holding the power button for more than 10 seconds) to rule out software crashes. If this is ineffective, disassemble the phone and check the screen cable. Clean the cable connector with an alcohol swab and reconnect it securely. If the problem persists, replace the entire screen assembly for testing. If the problem is resolved, it's a screen issue; otherwise, check the motherboard display chip and replace or repair the motherboard if necessary.

- Touch Malfunction Troubleshooting: First, clean the screen surface, turn off the phone, and restart it. If this is ineffective, enter the phone's "Developer Options" (required for some models) to perform touch calibration. Android users can use third-party calibration tools. Disassemble the phone and check the touch cable, clean it, and reinstall it. If the problem persists, replace the entire screen assembly.

- Screen Crack Repair: If only the outer screen is cracked and the inner screen is normal, the outer screen can be replaced separately (professional separation equipment is required to avoid damaging the inner screen); if the inner screen is damaged, the entire screen assembly must be replaced, ensuring that the parts are compatible with the phone model (e.g., Apple's original color screen requires the corresponding chip model, and Android curved screens require attention to curvature).

2. Battery-Related Faults: The Key to Battery Life and Safety

The battery is the core of a phone's battery life. Faults not only affect the user experience but may also pose safety hazards. Aging, bulging, and other issues require close attention.

(1) Common Symptoms and Causes

- Severely Reduced Battery Life: Mainly due to battery aging (significant capacity reduction after more than 500 cycles), excessive background applications (frequent screen wake-ups or CPU usage), abnormal battery calibration, and excessively low ambient temperature (lithium battery activity decreases below 0℃).

- Battery Bulging: Gas is produced by the decomposition of electrolyte inside the lithium battery. This is often caused by overcharging (keeping the battery fully charged for extended periods), using non-original chargers (unstable current and voltage), battery quality issues, or high-temperature environments. This is a dangerous fault and requires immediate attention.

- Automatic phone shutdown: Besides battery aging (insufficient capacity causing a sudden voltage drop), it could also be due to poor battery cable contact, a faulty motherboard power management chip, or insufficient battery power supply in low temperatures.

(2) Repair methods

- Troubleshooting decreased battery life: First, check the battery capacity using the phone's built-in "Battery Health" function (such as Apple, Huawei, Xiaomi, etc.). If it's below 80%, the battery needs to be replaced. If it's not below 80%, clear background apps, disable unnecessary location/Bluetooth/automatic synchronization functions, and perform battery calibration (fully discharge until automatic shutdown, then fully charge and keep charging for 1-2 hours). In low-temperature environments, it's recommended to use a warm phone case and avoid prolonged outdoor use.

- Battery Swelling Troubleshooting: Immediately stop using the phone. Avoid squeezing or impacting the bulging battery, and do not continue charging. Disassemble the phone and replace the battery with an original or brand-certified one. When replacing, ensure the following: First, disconnect the power (remove the motherboard power supply battery or disconnect the power interface before disconnecting the battery cable). Use a special pry tool to slowly separate the bulging battery (avoid puncturing the battery to prevent leakage or fire). After installing the new battery, check that the cable connection is secure and ensure the battery clips are fully engaged.

- Automatic Shutdown Repair: First, check the battery cable, clean the connector, and then reinsert it. Replace with a new battery and test. If the problem disappears, it's a battery issue. If the automatic shutdown persists, check the motherboard power management chip; repair or replace the motherboard if necessary.

Safety Tips: Always use original or brand-certified batteries that meet national standards when replacing the battery. Do not use refurbished or inferior batteries. Take proper insulation measures during operation to avoid short circuits.

3. Charging-Related Faults: Comprehensive Troubleshooting of the Power Supply Chain

Charging faults involve the charger, data cable, charging interface, battery, and motherboard. Troubleshooting should proceed step-by-step in the order of "peripherals - interfaces - internal components."

(1) Common Symptoms and Causes

- Unable to charge: Causes include charger/data cable damage (broken wire core, poor connector contact), dust/oxidation/damage to the charging port (prolonged plugging and unplugging causing bent or detached pins), poor battery cable contact or battery damage, and motherboard charging IC (charging management chip) malfunction.

- Extremely slow charging speed: Besides using non-original fast charging accessories (incompatible with the phone's fast charging protocol), this could also be due to poor charging port contact (unstable current transmission), too many background applications (high power consumption during charging), battery aging (decreased current receiving capacity), and motherboard fast charging chip malfunction.

- Phone gets extremely hot during charging: Primarily due to mismatched charger power (too high causing overload), poor charging port contact (excessive resistance generating heat), high-load background applications running (such as games or video calls), motherboard short circuit, or charging IC malfunction.

(2) Repair Methods

- Troubleshooting for Charging Failure: First, replace the charger and data cable with known working original ones to rule out peripheral issues. If charging still fails, use a flashlight to inspect the charging port and clean the inside of the port with a toothpick wrapped in alcohol to remove dust and oxides (be careful not to damage the pins). If the pins are bent, gently straighten them with tweezers. Disassemble the phone and inspect the battery cable and charging port cable, clean them, and reinstall them. Finally, check the motherboard charging IC; if damaged, replace the chip or the motherboard.

- Troubleshooting Slow Charging: Ensure you are using an original fast charging kit compatible with your phone (such as USB-C PD fast charging, Huawei SuperCharge, etc.); close background apps and avoid using the phone while charging; check the charging port contact and clean any dirt; if charging is still slow, replace the battery to rule out battery aging. Otherwise, repair the motherboard fast charging chip.

- Overheating during charging: Immediately stop charging, close background apps with high load, and place the phone in a well-ventilated area to cool down; replace the original charger and data cable; check the charging port and cable to rule out poor contact; if it is still hot after cooling, check if the motherboard is short-circuited or the charging IC is faulty, requiring professional motherboard repair.

4. Sound-related faults: Comprehensive inspection of audio output

Sound faults involve the earpiece, speaker, microphone, audio cable, and motherboard audio chip, requiring troubleshooting in scenarios such as calls and music playback.

(1) Common symptoms and causes

- No sound/low volume from the earpiece: Earpiece blockage (dust, oil buildup), earpiece damage (drop or water damage causing coil burnout), poor contact in the earpiece cable, motherboard audio chip failure.

- No sound/noise from the speaker: Speaker blockage (e.g., dust inside the bottom speaker), speaker damage (damaged diaphragm or faulty coil), loose speaker cable, motherboard audio chip failure.

- Microphone cannot pick up sound/hazy sound: Microphone hole blockage (dust, foreign object blockage), microphone damage, poor microphone cable contact, motherboard audio chip failure, and in some models, system permission settings may also cause this (e.g., the app does not have recording permission).

(2) Repair Methods

- Earpiece/Speaker Troubleshooting: First, check if the corresponding sound outlet is blocked, and clean the dust with a soft brush; adjust the volume and switch scenes when playing audio (e.g., test with a call using the earpiece, and test with music using the speaker) to rule out system volume setting issues; disassemble the phone and check the earpiece/speaker cable, clean it, and reinstall it; replace the earpiece/speaker and test. If the problem is resolved, it is a component issue; otherwise, repair the motherboard audio chip.

- Microphone Troubleshooting: First, clean the microphone hole (gently wipe with a toothpick wrapped with a small amount of alcohol, avoiding excessive penetration that could damage the microphone); go to the phone's "Settings - App Permissions" to ensure the corresponding app has recording permission; disassemble the phone and check the microphone cable and the microphone itself, and replace the microphone and test; if the problem persists, repair the motherboard audio chip.

5. System-Related Faults: Software-Level Troubleshooting and Repair

System faults are mostly caused by software conflicts, system vulnerabilities, and improper operation. Prioritize software-based repairs to avoid unnecessary hardware disassembly.

(1) Common Symptoms and Causes

- Phone Lag/Crash: Primarily caused by too many background applications (high memory usage), accumulated system junk files, outdated software versions (vulnerabilities), installation of malicious software or incompatible applications, or insufficient phone storage (less than 10% free space).

- Unable to Boot/Stuck on Boot Screen: Often caused by failed system updates (power outages or interruptions leading to corrupted system files), failed flashing, malicious software tampering with system files, or motherboard hardware failure (such as CPU or memory failure).

- App Crashes/Unable to Install: Caused by app version incompatibility with the system, corrupted app cache, insufficient phone storage, disabled system permissions, or phone virus infection.

(2) Repair Methods

- Lag/Freeze Troubleshooting: Force restart the phone to free up memory; go to "Settings - Application Management" to close unnecessary background applications, clear app cache and system junk; uninstall incompatible or malicious applications, update the phone system to the latest version; if storage is full, delete useless files or expand storage (e.g., insert an SD card on Android).

- Unable to Boot/Stuck on Boot Screen Repair: Android models can enter Recovery mode (the operation varies depending on the brand, e.g., long press the power button + volume up button on Xiaomi), clear the cache partition and restart; if ineffective, restore the system using official tools (e.g., Huawei Hisuie, Xiaomi MIUI flashing tool), remember to back up your data before flashing; Apple models can be flashed through iTunes recovery mode; if the phone still cannot boot after flashing, the motherboard hardware needs to be checked.

- App Crashing/Installation Troubleshooting: Update the app to the latest version, uninstall and reinstall; clear the app cache, grant the necessary permissions for the app; check the phone storage to ensure sufficient space; install mobile security software to scan for viruses, if infected, restore factory settings (back up your data before restoring).

6. Other Common Faults: Precise Handling of Detailed Issues

(1) Camera Fault

Symptoms: Unable to open the camera, blurry photos, camera app crashes, black spots in the image.

Repair: Clean dust and fingerprints from the camera lens; check the camera cable, clean and reinstall; replace the camera module for testing; if the fault persists, repair the motherboard's camera power supply chip or image processor.

(2) Wi-Fi/Bluetooth Fault

Symptoms: Wi-Fi cannot connect, frequently disconnects after connection, Bluetooth cannot pair, poor sound quality after Bluetooth connection.

Repair: Restart the router and phone, forget the Wi-Fi network and reconnect; check the phone's Wi-Fi/Bluetooth antenna (usually the metal spring at the top or bottom of the phone), clean and ensure good contact; update the system or restore network settings; replace the Wi-Fi/Bluetooth module (if integrated on the motherboard, the motherboard needs repair).

(3) Button Fault

Symptoms: Power button/volume button is stuck, unresponsive, loose.

Repair: Clean dust and foreign objects from the gaps between the buttons; disassemble and inspect the button springs and ribbon cables. Replace deformed springs and reinstall loose ribbon cables; replace the button assembly if the button base is damaged.

7. Core Repair Principles and Precautions

(1) Safety First: Power must be disconnected before disassembly to avoid short circuits; ensure proper insulation when replacing batteries, motherboards, and other components; wear insulated gloves and have fire extinguishers readily available when handling bulging batteries.

(2) Part Matching: Use original or brand-certified parts that are fully compatible with the phone model. Avoid using refurbished or assembled parts to ensure stable performance after repair (e.g., Apple screens must support True Tone display, and Android fast charging accessories must be compatible with the fast charging protocol).

(3) Troubleshooting Order: Follow the principle of "software first, hardware second; peripherals first, internal third." First, troubleshoot simple problems by restarting and debugging the software before disassembling and inspecting the hardware. Avoid blind disassembly.

(4) Data Backup: Before repair, always remind customers to back up important data, especially for operations such as flashing the ROM, restoring factory settings, and replacing the motherboard, to avoid data loss and disputes. 5. After-sales guarantee: Provide reasonable warranty periods for repaired phones (e.g., 6 months for the battery, 3 months for the screen), clearly define the warranty scope (non-human-caused damage is covered), and enhance customer trust.

The above summary covers over 90% of common faults in mobile phone repair. In actual repairs, adjustments should be made flexibly based on the specific model (e.g., Apple's True Tone restoration, Huawei's HarmonyOS adaptation) and the details of the fault, continuously accumulating experience to improve repair accuracy. At the same time, regularly check the official repair manuals and technical bulletins of various brands to stay abreast of the structural features and troubleshooting techniques of new models.