Narrative:

I am the shop owner and inspector. One of my mechanics was involved in installing an audio panel in a cessna P210N. He was having difficulty getting the cabin speaker to work; so I advised him to run new wiring to the cabin speaker. There were four wires to the speaker; I advised him to remove those wires and secure them and connect new wiring from the audio panel to the speaker. After completion of our work; the aircraft owner was on a flight and experienced an alternator failure (which was determined to be due to a failed alternator ground wire unrelated to the work we performed). While the aircraft was being repaired at a shop at the destination airport; the facility found the gear warning and stall warning horns were inoperative. I advised the aircraft's manager that I thought the gear/stall warning system was unrelated to the work our mechanic performed. After speaking with him; I remembered the four wires; and pulled the schematic to the cessna P210N. I realized at that point the system does indeed use a portion of the cabin speaker for stall warning. I am working with the mechanic at the airport where the plane is located to rectify the situation and get the gear warning repaired. Even though I didn't actually perform the work in question; I did give the bad information. I also signed off on the major alterations on this aircraft with my ia (inspection authorization) certificate; so I am responsible. The lesson I learned from this event is not to assume I know the systems; but to pull the schematics and look when performing an alteration. Thankfully; no one was hurt and no damage occurred to the airplane.

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Original NASA ASRS Text

Title: Aircraft Inspector provided erroneous information to Maintenance regarding repair of aircraft.

Narrative: I am the shop owner and inspector. One of my mechanics was involved in installing an audio panel in a Cessna P210N. He was having difficulty getting the cabin speaker to work; so I advised him to run new wiring to the cabin speaker. There were four wires to the speaker; I advised him to remove those wires and secure them and connect new wiring from the audio panel to the speaker. After completion of our work; the aircraft owner was on a flight and experienced an alternator failure (which was determined to be due to a failed alternator ground wire unrelated to the work we performed). While the aircraft was being repaired at a shop at the destination airport; the facility found the gear warning and stall warning horns were inoperative. I advised the aircraft's manager that I thought the gear/stall warning system was unrelated to the work our mechanic performed. After speaking with him; I remembered the four wires; and pulled the schematic to the Cessna P210N. I realized at that point the system does indeed use a portion of the cabin speaker for stall warning. I am working with the mechanic at the airport where the plane is located to rectify the situation and get the gear warning repaired. Even though I didn't actually perform the work in question; I did give the bad information. I also signed off on the major alterations on this aircraft with my IA (Inspection Authorization) certificate; so I am responsible. The lesson I learned from this event is not to assume I know the systems; but to pull the schematics and look when performing an alteration. Thankfully; no one was hurt and no damage occurred to the airplane.

Data retrieved from NASA's ASRS site 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.