Solution to Error E21 on Bamboo Printer: Diagnosis and Repair of the Temperature Sensor
When your Bamboo printer displays the E21 code, it is alerting you to a critical issue with the temperature sensor of the hot bed. This failure occurs because the thermistor is disconnected or has a short circuit, preventing the system from correctly reading thermal values. As a safety measure, the machine stops automatically to avoid major damage to components. 🛑
Initial Verification of Thermistor Connections
The first step to resolve the error E21 is to thoroughly inspect the sensor wiring connections. Completely disconnect the printer from the power supply and visually check the connector on the mainboard, ensuring it is firmly inserted. Examine the entire cable path for evident physical damage, such as cuts, crushes, or burn marks that could cause a short circuit. If you find a loose connector, reconnect it properly and perform a test to check if the error persists. 🔍
Key steps in verification:- Total disconnection of electrical power to ensure safety during inspection
- Visual inspection of the connector on the mainboard and along the wiring path
- Search for physical damage such as cuts, burns, or exposed wires that could cause short circuits
Patience and meticulousness in the initial inspection can save you more complex and costly procedures.
Precise Diagnosis with Multimeter
If the connections appear to be in good condition, the next step is to check the thermistor using a multimeter. Set the instrument to resistance measurement mode (ohms) and place the probes on the two contacts of the sensor. A properly functioning thermistor should show values between 80K and 120K ohms at room temperature. If you get an open circuit reading (infinite resistance), it indicates the sensor is internally disconnected. Conversely, if the measurement shows zero ohms or an extremely low resistance, it confirms the presence of a short circuit in the component. In either case, the definitive solution is to replace the thermistor with a new one. 📊
Multimeter measurement procedure:- Multimeter setup in ohms mode to measure electrical resistance
- Correct placement of probes on the thermistor sensor contacts
- Interpretation of readings: normal values (80K-120KΩ), open circuit (infinite) or short circuit (0Ω)
Replacement of the Faulty Thermistor
To replace the damaged thermistor, it is essential to acquire a compatible replacement specifically for the Bamboo model. Carefully remove the hot bed following the user manual instructions, locate the sensor adhered to the underside surface, and disconnect its wires. Apply gentle heat with a heat gun to soften the adhesive holding the thermistor, carefully detach it, and place the new sensor in the exact same position. Secure the wiring properly to avoid strain and reinstall the hot bed, meticulously verifying that all connections are correctly established before powering on the printer again. 🛠️
Often, the biggest obstacle is not the technical complexity of the repair, but the fear of disassembling equipment that seems complicated. In reality, these procedures only require patience, basic tools, and following detailed tutorials available on platforms like YouTube. The satisfaction of repairing your own printer and the economic savings make it worth overcoming that initial apprehension. 💪