What Are Common Controller Errors?

Hot runner temperature controllers depend on thermocouple signals to maintain stable heating, making thermocouple faults the most common source of error codes. Understanding these errors allows quick troubleshooting, reduces downtime, and prevents defective production. The most frequent error is TC ERR, which generally indicates an open circuit. This occurs when the thermocouple wire is broken, disconnected, or the probe is damaged. Mold vibration, high-temperature aging, and mechanical stress are the main causes. When this error appears, the system typically stops heating to prevent overheating. Another common issue is short circuit, meaning thermocouple wires contact each other or the grounded mold body. Short circuits cause abnormal readings and may damage the controller. Damaged insulation or crushed cables are typical causes. Reverse polarity is a frequent installation mistake where positive and negative wires are swapped, resulting in negative temperature displays or uncontrolled heating. Correcting the wiring usually resolves the problem immediately. Over-temperature alarms often result from thermocouple drift, probe displacement, or heater malfunction. If the thermocouple loses proper contact, it reads low temperatures, causing the controller to heat continuously until the safety limit is triggered. Low-temperature alarms occur when the detected temperature falls far below the set value, usually due to poor contact, heater failure, or faulty thermocouples. Signal interference appears as random, rapid temperature jumps without clear pattern. This is often caused by electromagnetic interference from heaters, motors, or unshielded cables running parallel to power lines. Ground loops worsen this problem. Sensor type mismatch occurs when the controller is set to K-type but a J-type thermocouple is connected, creating large deviations and unstable control. Some advanced controllers display specific codes for type mismatch. Communication errors may arise between the controller and terminal box, often caused by loose connectors or damaged lines. To resolve these errors, technicians follow a standard process: inspect the thermocouple for physical damage, check wiring polarity and connections, confirm type matching with the controller, test for short or open circuits, verify grounding, and replace faulty components if needed. Most errors can be fixed quickly with correct diagnosis. Understanding these common controller errors helps operators respond efficiently, minimize production interruptions, and maintain stable system performance.