A Mechanic with an assigned heavy workload performing Cabin Check Job Cards; was also instructed by his Lead Mechanic to Rob (Cannibalize) a passenger seat row from the A320 Coach section; and install the same seat on another A320. Lead said he would generate the necessary documents. Seat installed was later found to be of incorrect Effectivity.

Narrative

While working Overtime in December 2009; in Hangar 'A' on aircraft 'X' (A320); I was assigned to complete numerous Cabin Tasks; ie: Water Job Card; Seat Audio Job Card; and Cabin Final Checks. Aircraft 'X' was scheduled for Return to Service during my shift. After lunch I was instructed by my Lead Mechanic that seat assembly 6ABC was missing from coach and needed to be robbed from aircraft 'X' and installed on another A320; aircraft 'Y'; prior to my completion of the Seat Audio Video Job Card. My Lead also told me he would generate the Non-routines (Write-ups) for me to document my work and he would help me transport the seat from Hangar 'A' to Hangar 'D'. I removed the seat from aircraft 'X' and noted no discrepancies with seat. I transported and installed the robbed seat onto aircraft 'Y'; reference Maintenance Manual (MM) 25-21-41-401. I was unable to complete Seat Audio Video test due to ending of shift. No discrepancies were noted during seat installation. I was notified approximately eleven days later that the seat I installed on aircraft 'Y' was the incorrect Effectivity for the Airbus A320. I assumed the Lead that instructed me to the rob the seat had already checked proper Effectivity before requesting to rob the seat; as there were several Airbus aircraft in the Hangars to choose from.