Printhead Temperature Sensor (Thermistor) for Epson ET-8550 & XP-600 – Fix Error 031004 ET8550 XP600 THM

This thermistor serves as a temperature sensor inside the printhead. When it begins to fail or provide inaccurate readings, the printer can no longer detect temperature correctly.

As a result, the printer may:

• Falsely detect an overheating condition and shut down as a safety precaution, or
• Power on but display Error Code 031004, sometimes acting as if the printhead is not installed

In most cases, Error 031004 indicates that the printer cannot read a valid temperature signal from the printhead thermistor. However, this error is not always caused by the thermistor alone. It may also be triggered by a damaged FFC cable or a faulty mainboard, so proper diagnosis is essential before replacing parts.

This replacement thermistor is compatible with both Epson ET-8550 and XP-600 printheads, making it a reliable solution for restoring normal printer operation.

🔧 Common Symptoms

• Error code 031004
• Printer shuts down during startup
• False overheating warnings
• Printer fails to initialize or recognize the printhead

⚠️ Before Replacing the Thermistor

• To avoid unnecessary repairs, check the following:
• Inspect printhead FFC cables for ink/solution leakage, corrosion, or discoloration
• Ensure all FFC cables are fully inserted and securely connected
• Test with a known good printhead to confirm the mainboard is functioning properly

✅ What This Fix Does

• Restores accurate temperature readings
• Prevents false overheating shutdowns
• Helps the printer properly detect and initialize the printhead

📦 What's Included

• 1 × Thermistor (Temperature Sensor)

⚠️ Installation Notes (Advanced Repair)

• Requires printer disassembly and micro-soldering skills
• Not recommended for beginners
• Basic Steps Overview:
• Remove the printhead and unscrew the 4 screws to access the core
• Locate and desolder the faulty thermistor
• Carefully solder the replacement thermistor in place

💡 Compatibility

• Epson ET-8550 printhead
• Epson XP-600 printheada (including DTF and modified setups)

🛠️ Important Note

• Error 031004 can have multiple causes. While the thermistor is a common failure point, issues with the FFC cables, mainboard, or power circuitry may produce the same error. This part is intended for diagnostic and repair use.

🔄 BCH Technologies Insight

• Printers operate as complete systems. Replacing a single component may not fully resolve the issue if other parts are compromised. A full inspection is recommended for long-term reliability.