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#11
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OK, Thinking-Cap Time...
nrp wrote:
Jay - If you get desperate, you might be able to create this problem on the ground using a hand held or jury rigged electric motor to spin the alternator rather than having to run the engine. This would allow better diagnostic capability using an oscilloscope. If you try this, keep a fan blowing on the alternator. Even in cold temperatures, it will need cooling air. George Patterson If a tank is out of ammunition, what you have is a sixty ton portable radio. |
#12
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OK, Thinking-Cap Time...
Jay Honeck wrote:
last week seems to point to the all-to-common "mechanic-induced" squawk. It's not just mechanics. Any good troubleshooter knows you always look "where the human being was last". -- __!__ Jay and Teresa Masino ___(_)___ http://www2.ari.net/jmasino ! ! ! http://www.OceanCityAirport.com http://www.oc-Adolfos.com |
#13
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OK, Thinking-Cap Time...
I would check all the grounds in the system. That can cause this
problem. Along with a bad alternator switch. It causes the VR to not work properly. I had to bread each connection, clean it, then re-do it. ------------- Regards, Ross C-172F 180HP KSWI Jay Honeck wrote: Of course, we have a new squawk shortly after coming out of the shop. Perhaps someone here can point me in the right direction? Here's the scenario with our 1974 Piper Cherokee Pathfinder, with a 530 hour, normally aspirated Lycoming O-540-B4B5 engine: 1) Flying to Janesville, WI today. Extremely cold -- around 15 degrees Fahrenheit on the surface, near zero at altitude. The first real cold snap of the year. 2) In steady-state flight, both of us hear a "woo--woo--woo..." softly in the headphones. It sounds just like strobes that aren't grounded properly. 3) The noise slows down -- or speeds up -- in synch with the prop RPM. At 2300 RPM, it's going a bit faster than once per second -- maybe around three times every two seconds. 4) I switch our digital voltage/amperage meter to AMPs, and watch as it oscillates in time with the noise. It's alternating from 5 amps to 10-11 amps, in time with the "woo--woo--woo"... Voltage appears to be pretty steady at around 13.8-ish volts. 5) Adding load to the system (landing lights, fuel pump, etc.) makes the noise louder. Adding load to the system and then suddenly turning everything off makes the noise and amperage oscillation go away -- for about 30 seconds. It then returns. 6) Turning the alternator side of the split master switch ALSO makes the noise go away. It sometimes stays away when I turn the alternator back on. Sometimes it doesn't. 7) The battery is new this past summer. So, we've got a noise and amperage indication that can be corrected by adding load to the system -- and then suddenly taking it away. The noise is also fixed -- sometimes -- by cycling the alternator off and on. The service last week was having the impulse couplings serviced (per service bulletin), so electrical things have been tinkered with since our last flight. (This is ALWAYS when some new squawk seems to crop up.) Any ideas? Loose ground wire somewhere? Alternator failing? Any and all input is welcomed! Thanks! |
#14
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OK, Thinking-Cap Time...
OK, lets make that BREAK instead of bread.
------------- Regards, Ross C-172F 180HP KSWI Ross Richardson wrote: I would check all the grounds in the system. That can cause this problem. Along with a bad alternator switch. It causes the VR to not work properly. I had to bread each connection, clean it, then re-do it. ------------- Regards, Ross C-172F 180HP KSWI Jay Honeck wrote: Of course, we have a new squawk shortly after coming out of the shop. Perhaps someone here can point me in the right direction? Here's the scenario with our 1974 Piper Cherokee Pathfinder, with a 530 hour, normally aspirated Lycoming O-540-B4B5 engine: 1) Flying to Janesville, WI today. Extremely cold -- around 15 degrees Fahrenheit on the surface, near zero at altitude. The first real cold snap of the year. 2) In steady-state flight, both of us hear a "woo--woo--woo..." softly in the headphones. It sounds just like strobes that aren't grounded properly. 3) The noise slows down -- or speeds up -- in synch with the prop RPM. At 2300 RPM, it's going a bit faster than once per second -- maybe around three times every two seconds. 4) I switch our digital voltage/amperage meter to AMPs, and watch as it oscillates in time with the noise. It's alternating from 5 amps to 10-11 amps, in time with the "woo--woo--woo"... Voltage appears to be pretty steady at around 13.8-ish volts. 5) Adding load to the system (landing lights, fuel pump, etc.) makes the noise louder. Adding load to the system and then suddenly turning everything off makes the noise and amperage oscillation go away -- for about 30 seconds. It then returns. 6) Turning the alternator side of the split master switch ALSO makes the noise go away. It sometimes stays away when I turn the alternator back on. Sometimes it doesn't. 7) The battery is new this past summer. So, we've got a noise and amperage indication that can be corrected by adding load to the system -- and then suddenly taking it away. The noise is also fixed -- sometimes -- by cycling the alternator off and on. The service last week was having the impulse couplings serviced (per service bulletin), so electrical things have been tinkered with since our last flight. (This is ALWAYS when some new squawk seems to crop up.) Any ideas? Loose ground wire somewhere? Alternator failing? Any and all input is welcomed! Thanks! |
#15
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OK, Thinking-Cap Time...
Does it go away when you turn off the beacon?
Ammeter swings and a similar noise in my plane are due to the beacon's flasher. |
#16
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OK, Thinking-Cap Time...
OK, lets make that BREAK instead of bread.
So now we are breaking bread over our engines to fix problems? |
#17
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OK, Thinking-Cap Time...
OK, lets make that BREAK instead of bread.
So now we are breaking bread over our engines to fix problems? ("Darrel Toepfer" wrote) Is he in a jam or just buttering it over? What a crumby thing to say :-) Montwhitebread |
#18
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OK, Thinking-Cap Time...
Hope the alternator itself isn't toast!
Jim "Montblack" wrote in message ... OK, lets make that BREAK instead of bread. So now we are breaking bread over our engines to fix problems? ("Darrel Toepfer" wrote) Is he in a jam or just buttering it over? What a crumby thing to say :-) Montwhitebread |
#19
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OK, Thinking-Cap Time...
("Jim Burns" wrote)
Hope the alternator itself isn't toast! That's a half-baked assumption. Like those Capital One ads ...No, No, No. Any way you slice it, it's always the ground. ....cheaper that way. g Montblack |
#20
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OK, Thinking-Cap Time...
Dang, I should have read it before I published this....
------------- Regards, Ross C-172F 180HP KSWI john smith wrote: OK, lets make that BREAK instead of bread. So now we are breaking bread over our engines to fix problems? |
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