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peter(at)sportingaero.com
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 Posted: Sun Mar 22, 2015 2:01 pm Post subject: Charging failure - suggestions welcome |
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Dear All,
While flying today the low volts flasher came on - both volt meters
confirmed battery voltage only, and ammeter (measuring current delivered
by the alternator) showed zero. No big deal, we returned to the airport
and landed.
Predictably I did not have the time to investigate much, but there was
no evidence of a shredded/broken alternator belt - although I couldn't
verify it was definitely OK. I have now downloaded the EFIS data. It
shows the measured voltage dropped from the steady state 14.6v to 14v
over 21 seconds, with no change in current output, and then to 12.8v in
6 seconds with the current output dropping to zero.
Although I haven't suffered a charging failure before I am tempted to
say a broken belt would have lead a more rapid volts drop, so am
thinking that its either an internal alternator or voltage regulator
failure.
Can anyone with more experience suggest how I can determine if the
alternator or (external) voltage regulator has failed. I do not have a
spare of either to swap in. All suggestions gratefully accepted.
Regards, Peter
RV-6A Lyc O-320
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tim2542(at)sbcglobal.net
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| Posted: Sun Mar 22, 2015 2:57 pm Post subject: Charging failure - suggestions welcome |
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Assuming there is no mechanical damage, broken belt etc., the field circuit breaker isn't tripped, the next thing is look for is a broken "B" lead (large wire) or field wire. It seems fairly common for these to break at the alternator. Next thing then is figure out which wire is the field and does it have voltage on it while the engine is running. If you have voltage on the field terminal of the alternator but only battery voltage (~12 V), then the alternator is not working. If there is no field voltage then work the other way back to the regulator.
Good luck
Tim
| Quote: | On Mar 22, 2015, at 3:00 PM, Peter Pengilly <peter(at)sportingaero.com> wrote:
Dear All,
While flying today the low volts flasher came on - both volt meters confirmed battery voltage only, and ammeter (measuring current delivered by the alternator) showed zero. No big deal, we returned to the airport and landed.
Predictably I did not have the time to investigate much, but there was no evidence of a shredded/broken alternator belt - although I couldn't verify it was definitely OK. I have now downloaded the EFIS data. It shows the measured voltage dropped from the steady state 14.6v to 14v over 21 seconds, with no change in current output, and then to 12.8v in 6 seconds with the current output dropping to zero.
Although I haven't suffered a charging failure before I am tempted to say a broken belt would have lead a more rapid volts drop, so am thinking that its either an internal alternator or voltage regulator failure.
Can anyone with more experience suggest how I can determine if the alternator or (external) voltage regulator has failed. I do not have a spare of either to swap in. All suggestions gratefully accepted.
Regards, Peter
RV-6A Lyc O-320
|
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BobsV35B(at)aol.com
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| Posted: Sun Mar 22, 2015 3:35 pm Post subject: Charging failure - suggestions welcome |
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Barring an obvious broken wire, I generally find corrosion in a connection or high resistance in a switch or circuit breaker. The easiest check is to check the voltage while the system is operating. Check the voltage on each side of every connection while the system is working hard. Any drop at all across a CB, switch, or other connection is a bad thing! Those buggers do wear out and they do develop hard to measure resistance. Need to be checked while under load..
Happy Skies,
Old Bob
In a message dated 3/22/2015 5:58:23 P.M. Central Daylight Time, tim2542(at)sbcglobal.net writes:
| Quote: | --> AeroElectric-List message posted by: Tim Andres <tim2542(at)sbcglobal.net>
Assuming there is no mechanical damage, broken belt etc., the field circuit breaker isn't tripped, the next thing is look for is a broken "B" lead (large wire) or field wire. It seems fairly common for these to break at the alternator. Next thing then is figure out which wire is the field and does it have voltage on it while the engine is running. If you have voltage on the field terminal of the alternator but only battery voltage (~12 V), then the alternator is not working. If there is no field voltage then work the other way back to the regulator.
Good luck
Tim
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skywagon
Joined: 11 Feb 2006
Posts: 184
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| Posted: Sun Mar 22, 2015 6:33 pm Post subject: Charging failure - suggestions welcome |
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Hi Peter,
Others have mentioned the usual types of failures; broken field wire,
loose/dirty field connector, bad voltage regulator, etc.
One of the weirdest charging failures happened to me. . .
After a normal flight and visit, I fired up to return home and the charging
circuit appeared dead. I could watch the volt meter slowly go to bed with
the radios, etc. turned on. I was stuck in the boonies too. A dirt strip
in a vineyard and no one around . .
After testing the limited things I could and not finding the fault, I got
the battery fully charged with the help of a friend and made the short
flight home with 95% of the electrical bus shut down.
When I was home and had access to voltmeters, tools, etc. I chased the down
the fault after inventing new curse words, etc. and skinned hands.
Turned out the main bus CB (original factory unit in my '65 185) had opened
up without popping the indicator button. I was dumb-founded by that as it
was about the last thing I checked.
Thus, the charging system was fine doing its job, but, the charging current
could not get to the bus nor the battery.
Check the simple, easy things first and then move on to the un-obvious
subjects. . . .
David
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user9253
Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan
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| Posted: Sun Mar 22, 2015 6:56 pm Post subject: Re: Charging failure - suggestions welcome |
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Bob Nuckolls' book (Revision 12A) offers good advice on troubleshooting an alternator & regulator. See Appendix Z note 8.
Joe
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Joe Gores |
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user9253
Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan
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skywagon
Joined: 11 Feb 2006
Posts: 184
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| Posted: Mon Mar 23, 2015 8:17 am Post subject: Charging failure - suggestions welcome |
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Hi Joe,
Mine is dual range via push button. . .amps & volts.
D
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