A Mechanic reports reviewing some of his previous Maintenance actions and discovering a Rotable part had been Removed and Replaced (R/R) and added to his already closed Logbook page sign-off.

Narrative

I was assigned to work an Airbus Aircraft with a few other mechanics at the Hangar January 2010; on the second shift. I was to work the current APU MEL; 49-11-01. The aircraft was currently on MEL 49-11-01A for APU Bleed Air Inoperative. Before the aircraft arrived at the hangar that night; I found two AMM references that indicated that the reason the APU was on MEL was normal under certain conditions. I discussed my findings with Maintenance Controller Mr. 'X' and we decided that the MEL could be cleared with no further Maintenance action taken. I signed off the item on the Maintenance computer's work package for the Log page and made my MEL compliance statement on the Logbook page. I did not replace any part on the aircraft for this MEL. At the completion of my shift that day I began my weekend.Returning to work three days later; I reviewed some of my previous Maintenance actions to see if my 'fixes stayed fixed'. Reviewing the same Airbus and its APU history; I discovered a Rotable Part removal and installation was added to my closed Logbook page sign off. As I wrote earlier; I did not replace any part on that aircraft. In fact; examining the Serialized part history for the Part Number; showed I removed the part the day before I was even assigned to the aircraft.Another anomaly that caught my attention was the fact the part Removed and Replaced is an engine part and in no way related to the APU. Further review of ATA Chapters 75 and 36 showed no history of engine bleed work being accomplished on this aircraft during this time frame. The part removal information on Logbook page does not include a tracking number and no information is included as to the part being replaced per any accepted data. Noticing these discrepancies; I contacted the Maintenance Controller Manager on duty at that time; to take a look at the history with me. I do not know the cause of this problem at this time. I have insufficient information and everyone I have approached with this problem has helped to determine the cause but also have been unable. After notifying Duty Manager of the problems with my original sign off; he said he would make a call to 'a Maintenance computer system 'guru' to see if there could be a problem with the system and a plausible reason for the discrepancies. Later that day the Duty Manager informed me that the person he called could not explain the situation and that person called a third person in IT who also could not explain the problem. The Manager then told me to 'give it a few days' to see if an answer could be found. After not hearing anything 'for a few days'; I called Maintenance Control and spoke with Maintenance Controller Mr. 'Y' who was working the Airbus desk. I explained why I was calling and he remembered an issue with the same aircraft the previous week. He told me that prior to departure from ZZZ a week earlier; the Flight Crew heard an air leak from an engine that was later determined to be a bleed leak coming from the engine Precooler Heat Exchanger. The aircraft was placed on an estimated time for repairs; the part was ordered; replaced and it corrected the bleed leak. This was the same part that showed on my sign off. However; the APU bleed valve showed what was thought to be erroneous information and the aircraft was placed on MEL 49-11-01A. The aircraft departed on a ZZZ - ZZZZ - ZZZ round trip returning to ZZZ [the same day] when I was assigned to the aircraft. Mr.Y informed me that Maintenance Control records did not show anyone there reopening the Logbook and he could not explain the parts information entry; nor could he find any history of Maintenance work being accomplished in ATA chapters 36; 49 or 75 during this time frame; except the issuance of the APU MEL and my sign-off of that item. I then took this new information to my Supervisor. I explained the situation to him and he could not determine a reason for the discrepancies. He later talked with a third shift Supervisor; Mr.Z; who was on duty on the day [prior to my being assigned to the aircraft]; since it was the third shift that supposedly replaced the part. Mr Z did not provide any information since the Lead Mechanic on duty [that day earlier]; was on his days off. At this time I felt it necessary to submit this report for several reasons. First: if there is a problem with the data entry system and closed entries can be modified without any identifying tags or markers of who; when; or why the modification was made; this is a major flaw in our record keeping process. Second: it appears that undocumented Maintenance may have occurred which is a serious problem. Third: a satisfactory explanation has not been given to me regarding this situation and there does not seem to be a priority in finding one. Finally; and most importantly; the appearance of undocumented Maintenance has only my name attached to it and I did not; I repeat; did not remove; replace or do any other Maintenance to the aircraft except to clear an APU MEL using two AMM references. Without knowing the exact cause; I am unable at this time to offer any substantial suggestions as to preventing this situation in the future. For all Maintenance computer entries; only a portion of my employee file number is used.