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#1
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Transient alternator problem
"Jeremy Lew" wrote in message ... Was flying IFR in the clear on top of an overcast layer today. I noticed at some point that the ammeter was indicating zero, and not moving. The Alt warning light was not illuminated, except when I pressed the test button. I started to shut down non-essential electriconics in case this was for real. After a minute or two, the ammeter needle resumed normal indications, and stayed that way for the rest of the flight. The Alt warning light was properly illumated during low-RPM operations on the ground, as well as during the engine runup split switch check. The warning light/ammeter needle discrepancy suggests to me that problem was in the ammeter, and that the alternator was functioning normally the whole time. Anyone have any theories as to what would cause indications like this? Is external RF interference possible? (x-posted to rec.aviation.owning) What a coincidence, we've had the same sort of intermittent problem with our charging system on the last few flights! Of course, when we've had our voltmeter there to diagnose it, it seems to work perfectly Will let you know what we find-- please do likewise! (Ours is a 1978 Cessna 210M - IO520). Cheers, John Clonts Temple, Texas N7NZ |
#2
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Ours is a '78 Warrior (PA-28-151/161).
According to our maintenance officer, the ALT warning light and zero ammeter reading during low rpm (~1000) ground operations is actually not normal. It did make me pause for a minute, but then I figured I was being paranoid since I don't usually look at either of those indicators until the 2000 rpm runup, when both of those indicators were normal. We have a new alternator on order, I'll let you know what our outcome is too. Jeremy "John Clonts" wrote in message ... "Jeremy Lew" wrote in message ... Was flying IFR in the clear on top of an overcast layer today. I noticed at some point that the ammeter was indicating zero, and not moving. The Alt warning light was not illuminated, except when I pressed the test button. I started to shut down non-essential electriconics in case this was for real. After a minute or two, the ammeter needle resumed normal indications, and stayed that way for the rest of the flight. The Alt warning light was properly illumated during low-RPM operations on the ground, as well as during the engine runup split switch check. The warning light/ammeter needle discrepancy suggests to me that problem was in the ammeter, and that the alternator was functioning normally the whole time. Anyone have any theories as to what would cause indications like this? Is external RF interference possible? (x-posted to rec.aviation.owning) What a coincidence, we've had the same sort of intermittent problem with our charging system on the last few flights! Of course, when we've had our voltmeter there to diagnose it, it seems to work perfectly Will let you know what we find-- please do likewise! (Ours is a 1978 Cessna 210M - IO520). Cheers, John Clonts Temple, Texas N7NZ |
#3
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FWIW, on the '75 Archer I used to own, the ammeter needle would sometimes stick
against the faceplate and not move. The mechanic bent the needle a little bit so it wouldn't drag against the faceplate. The bent needle looked like crap, but it worked after that. Dave Jeremy Lew wrote: Ours is a '78 Warrior (PA-28-151/161). According to our maintenance officer, the ALT warning light and zero ammeter reading during low rpm (~1000) ground operations is actually not normal. It did make me pause for a minute, but then I figured I was being paranoid since I don't usually look at either of those indicators until the 2000 rpm runup, when both of those indicators were normal. We have a new alternator on order, I'll let you know what our outcome is too. Jeremy "John Clonts" wrote in message ... "Jeremy Lew" wrote in message ... Was flying IFR in the clear on top of an overcast layer today. I noticed at some point that the ammeter was indicating zero, and not moving. The Alt warning light was not illuminated, except when I pressed the test button. I started to shut down non-essential electriconics in case this was for real. After a minute or two, the ammeter needle resumed normal indications, and stayed that way for the rest of the flight. The Alt warning light was properly illumated during low-RPM operations on the ground, as well as during the engine runup split switch check. The warning light/ammeter needle discrepancy suggests to me that problem was in the ammeter, and that the alternator was functioning normally the whole time. Anyone have any theories as to what would cause indications like this? Is external RF interference possible? (x-posted to rec.aviation.owning) What a coincidence, we've had the same sort of intermittent problem with our charging system on the last few flights! Of course, when we've had our voltmeter there to diagnose it, it seems to work perfectly Will let you know what we find-- please do likewise! (Ours is a 1978 Cessna 210M - IO520). Cheers, John Clonts Temple, Texas N7NZ -- Dave Butler, software engineer 919-392-4367 |
#4
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My needle moved to zero during cruise flight, so I don't think it could be
the case for me. Jeremy "Dave Butler" wrote in message ... FWIW, on the '75 Archer I used to own, the ammeter needle would sometimes stick against the faceplate and not move. The mechanic bent the needle a little bit so it wouldn't drag against the faceplate. The bent needle looked like crap, but it worked after that. Dave Jeremy Lew wrote: Ours is a '78 Warrior (PA-28-151/161). According to our maintenance officer, the ALT warning light and zero ammeter reading during low rpm (~1000) ground operations is actually not normal. It did make me pause for a minute, but then I figured I was being paranoid since I don't usually look at either of those indicators until the 2000 rpm runup, when both of those indicators were normal. We have a new alternator on order, I'll let you know what our outcome is too. Jeremy "John Clonts" wrote in message ... "Jeremy Lew" wrote in message ... Was flying IFR in the clear on top of an overcast layer today. I noticed at some point that the ammeter was indicating zero, and not moving. The Alt warning light was not illuminated, except when I pressed the test button. I started to shut down non-essential electriconics in case this was for real. After a minute or two, the ammeter needle resumed normal indications, and stayed that way for the rest of the flight. The Alt warning light was properly illumated during low-RPM operations on the ground, as well as during the engine runup split switch check. The warning light/ammeter needle discrepancy suggests to me that problem was in the ammeter, and that the alternator was functioning normally the whole time. Anyone have any theories as to what would cause indications like this? Is external RF interference possible? (x-posted to rec.aviation.owning) What a coincidence, we've had the same sort of intermittent problem with our charging system on the last few flights! Of course, when we've had our voltmeter there to diagnose it, it seems to work perfectly Will let you know what we find-- please do likewise! (Ours is a 1978 Cessna 210M - IO520). Cheers, John Clonts Temple, Texas N7NZ -- Dave Butler, software engineer 919-392-4367 |
#5
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Had the same thing on the 182 about ten years ago. Drove me nuts for about a
week until I noticed that the throttle control was adjacent to the diode plate on the rear of the alternator. Spreading the two apart, you could clearly see where the throttle cable insulation was chafed through and touching the diode plate, killing the alternator. Of course, on the ground with the engine torque not moving the alternator just that few thousandths of an inch that made contact, it wouldn't do it for love nor money except when the airplane was actually flying. Run your hand all the way around the rear diode plate on the alternator and see if there is a cable nearby. Jim Jim Weir (A&P/IA, CFI, & other good alphabet soup) VP Eng RST Pres. Cyberchapter EAA Tech. Counselor http://www.rst-engr.com |
#6
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Dave Butler wrote in message ...
FWIW, on the '75 Archer I used to own, the ammeter needle would sometimes stick against the faceplate and not move. The mechanic bent the needle a little bit so it wouldn't drag against the faceplate. The bent needle looked like crap, but it worked after that. Dave The correct term (so as not to scare the uninitiated) is "formed" not "bent". Your mechanic "formed the needle a little bit". So it was explained to me by an ex-IBM ield engineer, anyway. John S. |
#7
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Alternator was removed and found to have worn brushes and somewhat corroded,
stiff springs. It was 5.5 years and 620 hours old, and was replaced with a new one. It is believed that the brush condition was responsible for the intermittant contact. Jeremy "John Clonts" wrote in message ... "Jeremy Lew" wrote in message ... Was flying IFR in the clear on top of an overcast layer today. I noticed at some point that the ammeter was indicating zero, and not moving. The Alt warning light was not illuminated, except when I pressed the test button. I started to shut down non-essential electriconics in case this was for real. After a minute or two, the ammeter needle resumed normal indications, and stayed that way for the rest of the flight. The Alt warning light was properly illumated during low-RPM operations on the ground, as well as during the engine runup split switch check. The warning light/ammeter needle discrepancy suggests to me that problem was in the ammeter, and that the alternator was functioning normally the whole time. Anyone have any theories as to what would cause indications like this? Is external RF interference possible? (x-posted to rec.aviation.owning) What a coincidence, we've had the same sort of intermittent problem with our charging system on the last few flights! Of course, when we've had our voltmeter there to diagnose it, it seems to work perfectly Will let you know what we find-- please do likewise! (Ours is a 1978 Cessna 210M - IO520). Cheers, John Clonts Temple, Texas N7NZ |
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