Narrative:

The aircraft had been down all day for an oil pressure indication problem. #2 engine oil pressure would fluctuate at and above rating detent. Swing shift changed a number of items with no help. When I arrived on grave shift; it was decided that we would change a relay in relay junction box 1 under the floor in the cabin. One of the leads found the part number for the relay. We picked it up in stores and installed it in the junction box. At that point swing shift left for the day. I installed the junction box; completed the operational checks and signed it off. It passed all of the operational checks in the aircraft maintenance manual (amm). This was quite some time ago; so I don't remember exactly who I was working with that night.apparently; a couple months later; the same aircraft started having the same problem. Another pilot wrote up the same discrepancy; oil pressure indication fluctuating at high power. That is when the relay was changed again; and it was discovered that I had installed the incorrect part number relay. The mechanic (who) worked that defect; apparently found the relay to not be the correct part number. The same mechanic corrected the discrepancy it at that time.to this day I cannot find the correct part number relay anywhere in the manuals. There is a green sheet in the wiring manual air traffic area-79; that says something about an engineering order; but I was not aware that green sheet existed at the time; and it isn't very clear as to what it means. In hindsight; I should have researched the part myself instead of taking someone's word for it; but the relay we installed matched the relay we removed which probably made me feel more comfortable with installing this relay. Although; if I had researched it myself; I'm not sure I would have been able to find the correct relay in the manual. I find the green sheet in air traffic area-79; of the wiring manual to be unclear. Other than that; I need to be more vigilant in ensuring that the parts I'm installing are correct and effective to that aircraft.

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Original NASA ASRS Text

Title: A Line Mechanic reports he installed a relay under the cabin floorboard of a DHC-8-400; for an oil pressure indication problem on #2 engine. The same problem resurfaced a couple of months later; and the relay he installed was found to be an incorrect part.

Narrative: The aircraft had been down all day for an oil pressure indication problem. #2 engine oil pressure would fluctuate at and above rating detent. Swing shift changed a number of items with no help. When I arrived on grave shift; it was decided that we would change a relay in relay junction box 1 under the floor in the cabin. One of the Leads found the part number for the relay. We picked it up in stores and installed it in the junction box. At that point swing shift left for the day. I installed the junction box; completed the operational checks and signed it off. It passed all of the operational checks in the Aircraft Maintenance Manual (AMM). This was quite some time ago; so I don't remember exactly who I was working with that night.Apparently; a couple months later; the same aircraft started having the same problem. Another Pilot wrote up the same discrepancy; oil pressure indication fluctuating at high power. That is when the relay was changed again; and it was discovered that I had installed the incorrect part number relay. The Mechanic (who) worked that defect; apparently found the relay to not be the correct part number. The same Mechanic corrected the discrepancy it at that time.To this day I cannot find the correct part number relay anywhere in the manuals. There is a green sheet in the wiring manual ATA-79; that says something about an engineering order; but I was not aware that green sheet existed at the time; and it isn't very clear as to what it means. In hindsight; I should have researched the part myself instead of taking someone's word for it; but the relay we installed matched the relay we removed which probably made me feel more comfortable with installing this relay. Although; if I had researched it myself; I'm not sure I would have been able to find the correct relay in the manual. I find the green sheet in ATA-79; of the wiring manual to be unclear. Other than that; I need to be more vigilant in ensuring that the parts I'm installing are correct and effective to that aircraft.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.