Narrative:

We departed in a C182RG on an IFR flight plan to perform an ipc. I was flying and was accompanied by a cfii. We contacted departure and were cleared direct to [several fixes]; then cleared straight in to the ILS 29. During cruise I programmed the approach into the GNS530 and coupled the autopilot; intending to have the autopilot fly to the final approach fix (FAF). The flight had been normal to that point. I began a descent and captured the localizer on NAV1. After turning onto the final approach course; and while descending into IMC; the GNS530 flickered briefly; then went dark and displayed an 'initializing' message on the screen. Shortly after that the MX20 multi-functional display (mfd) also went dark. NAV2 was unaffected so I continued to fly the localizer while the PNF executed the troubleshooting checklist. During that time; the SL70 transponder began flashing 'fail' in its squawk code display; then COM2 failed. We were at approximately 1;800 feet and below the clouds; which I would estimate had bases of approximately 2;500 feet. We maintained that altitude; aborted the approach; and turned back towards our departure airport. After a few minutes more troubleshooting; we elected to attempt a precautionary landing at [a nearby alternate airport]. While on final approach; we were unable to confirm that the gear were fully locked so I went around and we followed the emergency gear extension procedure. We were unable to lock the gear so we orbited for some additional troubleshooting. During this time; COM2 began operating and we were able to contact approach and inform them of our situation. We then got a low voltage caution. I reset the alternator breaker; which resolved the low voltage indication. The PNF tried powering the GNS530 back on and it took power; but then dropped offline again. We contacted approach to cancel IFR and proceeded VFR to [departure airport]; maintaining radio contact with them until we landed.during the flight there were no warnings or indicators of the impending failure. During preflight the alternator belt was inspected and found to be intact; and it was still intact after the flight. This airplane was grounded [on an earlier occasion] because the renter found that the battery had insufficient power to crank the starter. Other than that I am not aware of any other known problems with the aircraft electrical system. Because we were able to maintain VFR flight after our descent; I did not feel it was risky to continue troubleshooting in flight; as we were near an airport; had plenty of fuel; and were in an area with no significant terrain or obstacles. I believe that the alternator trip off was caused by extending and retracting the gear. The gear appeared to be locked when we extended it manually but because we couldn't verify it; we elected not to attempt a landing until we could confirm the gear down.

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Original NASA ASRS Text

Title: A C182 pilot on an instrument check flight with a flight instructor reported the loss of several electrical components; likely due to a faulty voltage regulator.

Narrative: We departed in a C182RG on an IFR flight plan to perform an IPC. I was flying and was accompanied by a CFII. We contacted departure and were cleared direct to [several fixes]; then cleared straight in to the ILS 29. During cruise I programmed the approach into the GNS530 and coupled the autopilot; intending to have the autopilot fly to the Final Approach Fix (FAF). The flight had been normal to that point. I began a descent and captured the localizer on NAV1. After turning onto the final approach course; and while descending into IMC; the GNS530 flickered briefly; then went dark and displayed an 'INITIALIZING' message on the screen. Shortly after that the MX20 Multi-Functional Display (MFD) also went dark. NAV2 was unaffected so I continued to fly the localizer while the PNF executed the troubleshooting checklist. During that time; the SL70 transponder began flashing 'FAIL' in its squawk code display; then COM2 failed. We were at approximately 1;800 feet and below the clouds; which I would estimate had bases of approximately 2;500 feet. We maintained that altitude; aborted the approach; and turned back towards our departure airport. After a few minutes more troubleshooting; we elected to attempt a precautionary landing at [a nearby alternate airport]. While on final approach; we were unable to confirm that the gear were fully locked so I went around and we followed the emergency gear extension procedure. We were unable to lock the gear so we orbited for some additional troubleshooting. During this time; COM2 began operating and we were able to contact approach and inform them of our situation. We then got a low voltage caution. I reset the alternator breaker; which resolved the low voltage indication. The PNF tried powering the GNS530 back on and it took power; but then dropped offline again. We contacted approach to cancel IFR and proceeded VFR to [departure airport]; maintaining radio contact with them until we landed.During the flight there were no warnings or indicators of the impending failure. During preflight the alternator belt was inspected and found to be intact; and it was still intact after the flight. This airplane was grounded [on an earlier occasion] because the renter found that the battery had insufficient power to crank the starter. Other than that I am not aware of any other known problems with the aircraft electrical system. Because we were able to maintain VFR flight after our descent; I did not feel it was risky to continue troubleshooting in flight; as we were near an airport; had plenty of fuel; and were in an area with no significant terrain or obstacles. I believe that the alternator trip off was caused by extending and retracting the gear. The gear appeared to be locked when we extended it manually but because we couldn't verify it; we elected not to attempt a landing until we could confirm the gear down.

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.