cowman
Final Approach
Aircraft is a 78 Piper Archer II
Cliff Notes Version:
Had an alternator failure on my long cross country earlier this year. Turning field switch off then on again would temporarily fix it but it would come back in shorter intervals. Had the voltage regulator replaced and it seemed to have fixed it. Flown another 15-ish flight hours and now annunciator light came on and no charge on ammeter. Turning field off/on no longer fixed it but after landing the light went off and it showed charging. Mechanic replaced brushes in alternator but on test flight the light came on again just after rotation with no charge. Landed and after landing light is off and alternator is charging again. Going to talk to mechanic again tomorrow.
Full Narrative:
Earlier this year on my trip out to CA I had an alternator failure in flight... I didn't notice the annunciatior light(I assume) because I was busy negotiating LAX area traffic, it was bright and sunny out, and the light is pretty dim when there's an actual problem. First sign was when my panel shutdown mid-transmission with ATC. I tried turning the master switch off then on again which resulted in everything coming back up... ammeter shot somewhere over 35(35 is the middle and about where it sits for a minute after startup before dropping). Everything worked fine after that point, I got back in touch with ATC and completed the flight ~45min. As one would expect the ammeter slowly came down to it's normal position about 1/4 of the way up between the 0 and 35 marks. On the ground I tried turning on everything electrical, running the airplane up, etc and could not reproduce the problem.
As there was no mx available where I was, it was a VFR day, and I couldn't reproduce the issue I chose to move on to my next stop. Shortly after leveling off the annunciator light came on and the ammeter dropped to 0. I turned the alternator field switch only off then back on and once more the annunciator turned off and the ammeter showed a charge. A few minutes later again the light comes on and no charge so I reset it.... repeated this several more times with the interval getting shorter each time until it wouldn't reset. I landed short of my destination in Yuma, AZ. After a weekend of messing around culminating in an alternator shop bench testing the alternator and verifying it showed it was outputting full power I limped on into to Chandler, AZ where a shop was able to replace my voltage regulator. After the voltage regulator was replaced the issue seemed to have been solved... I flew all the way home with no issues and made a couple more flights after that again with no issues.
Now, I should mention here that I'd consulted with some Piper owner's groups and they'd suspected an overvoltage protection relay to be the problem and that certainly seemed to match the symptoms... as the battery got all the way charged up the alternator would stop working. On the way to chandler I tested that theory by turning the field off for 5+ minutes before turning it back on and indeed it would stay charging longer if I did that. I couldn't find this overvoltage relay though and was informed by the shop at Chandler that by my model year of Cherokee it had been integrated into a single unit with the voltage regulator- so if this is all correct both things were replaced and as I said it seemed to have been fixed.... at least for the next 10-20 hours of flight time.
So flight before last on the way home my alt light comes on again and ammeter at 0. Here we go again. This time turning the field off/on again doesn't seem to help. I made it home and noticed around the time I landed my alternator was charging again, seeming to be at full output. I talked to my mechanic and he was pretty sure the brushes in the alternator must be worn out so he replaced them.
Just got a chance to do a test flight today- a week later. Airplane started up, taxied out, did a runup, no trouble. Then just after rotation the god forsaken alt light is on again and ammeter at 0. Alt field reset does nothing. Stayed in the pattern, landed, noted after landing the light is off and ammeter shows charging again. Mechanic had gone home for the day so I left a note. Looking for suggestions.
Cliff Notes Version:
Had an alternator failure on my long cross country earlier this year. Turning field switch off then on again would temporarily fix it but it would come back in shorter intervals. Had the voltage regulator replaced and it seemed to have fixed it. Flown another 15-ish flight hours and now annunciator light came on and no charge on ammeter. Turning field off/on no longer fixed it but after landing the light went off and it showed charging. Mechanic replaced brushes in alternator but on test flight the light came on again just after rotation with no charge. Landed and after landing light is off and alternator is charging again. Going to talk to mechanic again tomorrow.
Full Narrative:
Earlier this year on my trip out to CA I had an alternator failure in flight... I didn't notice the annunciatior light(I assume) because I was busy negotiating LAX area traffic, it was bright and sunny out, and the light is pretty dim when there's an actual problem. First sign was when my panel shutdown mid-transmission with ATC. I tried turning the master switch off then on again which resulted in everything coming back up... ammeter shot somewhere over 35(35 is the middle and about where it sits for a minute after startup before dropping). Everything worked fine after that point, I got back in touch with ATC and completed the flight ~45min. As one would expect the ammeter slowly came down to it's normal position about 1/4 of the way up between the 0 and 35 marks. On the ground I tried turning on everything electrical, running the airplane up, etc and could not reproduce the problem.
As there was no mx available where I was, it was a VFR day, and I couldn't reproduce the issue I chose to move on to my next stop. Shortly after leveling off the annunciator light came on and the ammeter dropped to 0. I turned the alternator field switch only off then back on and once more the annunciator turned off and the ammeter showed a charge. A few minutes later again the light comes on and no charge so I reset it.... repeated this several more times with the interval getting shorter each time until it wouldn't reset. I landed short of my destination in Yuma, AZ. After a weekend of messing around culminating in an alternator shop bench testing the alternator and verifying it showed it was outputting full power I limped on into to Chandler, AZ where a shop was able to replace my voltage regulator. After the voltage regulator was replaced the issue seemed to have been solved... I flew all the way home with no issues and made a couple more flights after that again with no issues.
Now, I should mention here that I'd consulted with some Piper owner's groups and they'd suspected an overvoltage protection relay to be the problem and that certainly seemed to match the symptoms... as the battery got all the way charged up the alternator would stop working. On the way to chandler I tested that theory by turning the field off for 5+ minutes before turning it back on and indeed it would stay charging longer if I did that. I couldn't find this overvoltage relay though and was informed by the shop at Chandler that by my model year of Cherokee it had been integrated into a single unit with the voltage regulator- so if this is all correct both things were replaced and as I said it seemed to have been fixed.... at least for the next 10-20 hours of flight time.
So flight before last on the way home my alt light comes on again and ammeter at 0. Here we go again. This time turning the field off/on again doesn't seem to help. I made it home and noticed around the time I landed my alternator was charging again, seeming to be at full output. I talked to my mechanic and he was pretty sure the brushes in the alternator must be worn out so he replaced them.
Just got a chance to do a test flight today- a week later. Airplane started up, taxied out, did a runup, no trouble. Then just after rotation the god forsaken alt light is on again and ammeter at 0. Alt field reset does nothing. Stayed in the pattern, landed, noted after landing the light is off and ammeter shows charging again. Mechanic had gone home for the day so I left a note. Looking for suggestions.