scope:

Description of Driving Event:

While performing electrical checkout of a newly manufactured electronic component, erratic highcurrent measurements were noticed. Some technicians in the area believed they also occasionally smelled something burning. While a drawer was removed for other troubleshooting, it was noticed that the wires connected to a contactor were loose. After removing the contactor cover, overheating of the lugged wires and nut/bolt connection was obvious; there was discoloration typical of high temperatures. The contactor cover was also slightly melted and burned. This high-resistance connection caused overheating when large currents were flowing. The wire lugs were welded to the bolt and the nut could not be removed (or tightened). The contactor had to be replaced and the wires re-lugged. Root cause: Nut tightness check was missed during in-process assembly inspection. The company that assembled the console did not tighten the contactor wires. The nut was spun on to the bolt, but it was not even finger tight.