Maintenance Airframe; Maintenance Powerplant
Situational Awareness; Time Pressure; Human-Machine Interface
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Aircraft Aircraft Damaged; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Human Factors; Procedure
After completing work on an interior log item on Aircraft X; I checked the flight deck to make sure the battery was off. I found the battery on and switched it to off not realizing the APU was running at the time. I then called my Lead to make sure it was OK to leave the battery off; but he told me the plane was leaving soon and to leave the battery on. I put the battery back on; then immediately left the aircraft and returned to the ready room and told my Lead I was off the aircraft. A few minutes later we got word that there was a fire in the tail area of aircraft X.
Technician reported turning the aircraft battery switch to off with the APU running; then turning the battery switch back to on a B757. Later it was reported that there was a fire in the APU compartment.