Re: Transient alternator problem

[John Clonts]

"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

[Jeremy Lew]

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]

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

[Jeremy Lew]

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
>

[Jim Weir]

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

[John Stevens]

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.

[Jeremy Lew]

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
>
>
>