Siemens Drive Fault Code 7902

Scenario: A automotive paint line conveyor trips with F07902 every Monday morning but runs fine for the rest of the week.

Investigation: Technicians found no cable breaks. The motor windings tested OK. The clue was the timing – every Monday after weekend shutdown. siemens drive fault code 7902

Root Cause: A magnetic contactor between the drive and motor had a pitted auxiliary contact that overheated slightly on the first start of the week, dropping one phase for 50ms. As the day progressed, thermal expansion improved contact – until the next Monday. Scenario: A automotive paint line conveyor trips with

Solution: Replaced contactor and implemented weekly starter torque check. Fault 7902 eliminated. When fault 7902 appears, do not simply reset and restart

To avoid future occurrences of fault code 7902:

When fault 7902 appears, do not simply reset and restart. Follow this systematic diagnostic sequence.