Why Do Hot Runner Thermocouples Fail Frequently?

Thermocouple failure is a common problem in hot runner systems, leading to temperature deviation, production interruption, and high scrap rates. Typical failures include open circuit, short circuit, signal drift, slow response, physical damage, and poor contact. Open circuits usually result from broken internal wires, loose terminals, or over‑tightening during installation. Short circuits occur when insulation is damaged by high temperature, corrosion, or mechanical extrusion. Signal drift is mainly caused by junction aging, material contamination, or long‑term thermal fatigue. Slow response comes from poor thermal contact, improper installation depth, or excessive oxide layer on the probe surface. Physical damage includes bending, breaking, or wear caused by improper operation, mold clamping, or material erosion. Many failures originate from human factors such as incorrect wiring, mismatched Type K/J sensors, rough cable routing, and lack of regular maintenance. Harsh working conditions such as ultra‑high temperature, chemical corrosion, strong vibration, and thermal shock also accelerate sensor aging. To reduce failures, users must follow standard installation procedures, avoid forced bending, ensure sufficient insertion depth, and regularly check cables and connectors. Correct troubleshooting methods include multimeter measurement, visual inspection, insulation testing, and calibration verification. Understanding failure causes and solutions helps maintenance teams quickly locate problems, reduce downtime, and extend thermocouple service life. Preventive maintenance is more effective than emergency repair, helping enterprises maintain stable production and reduce operational costs.