Narrative:

[Flying] IFR to destination. Avionics [later] became intermittent; but continued to function. After hand-off to ATC; [avionics] system began to fail. Over the river I lost my panel; and then comms. I used my hand-held to communicate with airport ZZZ ATC/tower. Since I would have to drop gear manually; had no indicator lights; no mode C; and was using a hand-held. ZZZ tower instructed a fly-by and confirmed gear was down; but uncertain whether locked. I landed runway 14 without further incident.I was able to locate a mechanic [the] following day who looked for the cause. He discovered that the battery terminals and cables were significantly corroded; that the positive connection was installed without a washer and lock-washer; and; that a wingnut was loose in the compartment. The annual was signed off in july 2014. The battery was serviced as part of the annual and the log sticker reflects a battery expiration date of december 2015.I subsequently learned as a result of the july 2015 annual (by a different a&P) that the new alternator had been installed incorrectly during the prior annual. The mechanic who performed the current annual found solid copper core 16-gauge hvac electrical wiring had been used to ground the alternator. The alternator was a case ground unit. The oem repaired the alternator free of charge even though the warranty had expired because the unit had so few hours on it and shouldn't have failed. The current annual also revealed that the #1 cylinder had been mounted with connecting rod nuts. I have the wiring and the connecting rod nuts in my possession.

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Original NASA ASRS Text

Title: After loss of forward display panel and then all communications; pilot used hand-held phone to communicate with ATC/Tower and diverts his Piper PA32-301R. With no indicator lights; no Mode C; landed after performing fly-by to confirm landing gears down. Battery terminals found to be significantly corroded and not secured correctly. Previous Annual Inspection found to be deficient.

Narrative: [Flying] IFR to destination. Avionics [later] became intermittent; but continued to function. After hand-off to ATC; [avionics] system began to fail. Over the river I lost my panel; and then COMMS. I used my hand-held to communicate with Airport ZZZ ATC/Tower. Since I would have to drop gear manually; had no indicator lights; no Mode C; and was using a hand-held. ZZZ Tower instructed a fly-by and confirmed gear was down; but uncertain whether locked. I landed Runway 14 without further incident.I was able to locate a Mechanic [the] following day who looked for the cause. He discovered that the battery terminals and cables were significantly corroded; that the positive connection was installed without a washer and lock-washer; and; that a wingnut was loose in the compartment. The Annual was signed off in July 2014. The battery was serviced as part of the Annual and the log sticker reflects a battery expiration date of December 2015.I subsequently learned as a result of the July 2015 Annual (by a different A&P) that the new alternator had been installed incorrectly during the prior Annual. The Mechanic who performed the current Annual found solid copper core 16-gauge HVAC electrical wiring had been used to ground the alternator. The alternator was a case ground unit. The OEM repaired the alternator free of charge even though the warranty had expired because the unit had so few hours on it and shouldn't have failed. The current Annual also revealed that the #1 cylinder had been mounted with connecting rod nuts. I have the wiring and the connecting rod nuts in my possession.

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.