Wire open breakage and gradual measuring drift are two most frequent thermocouple faults on YUDO, Husky and domestic hot runner systems, with partial similar abnormal display phenomenon but completely different troubleshooting and replacement solutions; mastering scientific distinguishing test method helps maintenance technicians cut unnecessary spare part cost and reduce blind repeated disassembly workload on production site. Complete core wire breakage forms thorough open-circuit state, most mainstream hot runner temperature controllers instantly display fixed ultra-high or ultra-limit abnormal temperature value which never follows real hot runner temperature change during heating or cooling process, no numerical fluctuation alongside actual mold temperature rise and fall is the most intuitive identification feature of wire fracture open fault. In contrast, measuring drift caused by alloy aging, probe dirt accumulation or sheath corrosion presents slow continuous numerical offset; displayed reading still synchronously changes following hot runner actual temperature fluctuation but always keeps fixed deviation away from standard true temperature value.
Portable multimeter millivolt measurement is efficient auxiliary on-site discrimination means: shift multimeter to millivolt range and connect thermocouple cold end two terminals; heat probe with hot air gun artificially, no millivolt potential output indicates inner core wire broken needing direct sensor replacement; continuously varying normal millivolt signal proves wire intact and fault source locates at measuring drift from aging or surface dirt, feasible to recover precision via probe cleaning or controller parameter compensation instead of spare part replacement.
Novice maintenance personnel often confuse two faults and blindly replace intact thermocouple for drift failure, causing unnecessary spare part waste and production interruption. Standard workshop operation adds multimeter pre-test item before sensor removal to confirm fault type. Regular periodic cleaning of probe surface oxide and carbon deposit effectively reduces drift occurrence rate and prolongs thermocouple service life of whole hot runner system.
