Maintenance Airframe; Maintenance Powerplant
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Procedure
Plane came in with PROX SYS 1 fault. Went through MDC (Maintenance Data Computer) to isolate which PROX sensor was faulting. After confirming [the] fault; [the] aircraft was sent to [the] hangar. [I] jacked [up the] aircraft and upon closer and more proper inspection of target; [I] found that it was installed backward. This caused the target to be a lot closer to the sensor. After comparing it to the adjacent targets and confirming with tech data; we concluded that the target was definitely installed incorrectly.Because the aircraft only recently exited from heavy check; we assume it happened during that process as it could easily be overlooked. [I] removed [the] target; flipped it; re-installed; and performed all adjustments and operation checks in accordance with all [of] the appropriate tech data. It is not uncommon to see planes exit heavy check with small mishaps causing big problems and thereby delays. There could perhaps be a more thorough process in order to return these aircraft to service.
Technician reported a proximity switch target that was improperly installed during the heavy check process; caused a #1 System Prox Fault.