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Transient alternator problem



 
 
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  #1  
Old July 7th 04, 12:05 AM
Jeremy Lew
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Posts: n/a
Default Transient alternator problem

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?

Thanks,
Jeremy


  #2  
Old July 7th 04, 03:08 AM
Nathan Young
external usenet poster
 
Posts: n/a
Default

On Tue, 6 Jul 2004 19:05:22 -0400, "Jeremy Lew"
wrote:

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?


What kind of plane & what year?
  #3  
Old July 7th 04, 04:01 AM
John Clonts
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Posts: n/a
Default


"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



  #4  
Old July 7th 04, 01:38 PM
Jeremy Lew
external usenet poster
 
Posts: n/a
Default

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





  #5  
Old July 7th 04, 01:41 PM
Dave Butler
external usenet poster
 
Posts: n/a
Default

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

  #6  
Old July 7th 04, 05:19 PM
Jeremy Lew
external usenet poster
 
Posts: n/a
Default

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



  #7  
Old July 7th 04, 06:40 PM
Jim Weir
external usenet poster
 
Posts: n/a
Default

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
  #8  
Old July 7th 04, 09:41 PM
Robert M. Gary
external usenet poster
 
Posts: n/a
Default

"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?



I've had the same problem in my Mooney. Sometimes the buss voltage
drops down to just 13v sometimes to 12v but then comes back. It
appears the problem is an old master switch. The contacts on the
switch wear out and if the alternator does not get full battery
voltage from the field (going through the master switch) it will put
out less voltage. The contacts are a bit intermitant sometimes as they
get corrosion.

-Robert
  #9  
Old July 8th 04, 01:46 AM
Martin Kosina
external usenet poster
 
Posts: n/a
Default

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.


Hmmm - I thought the ammeter *should* indicate zero when the battery
is fully charged and the electrical load is not changing ? What is the
"normal" indication you are refering to ?
  #10  
Old July 8th 04, 02:34 AM
Jeremy Lew
external usenet poster
 
Posts: n/a
Default

I've never seen our ammeter reading zero before. Doesn't any load on the
battery mean constant discharge and therefore constant charge for the
alternator? Normally, the needle is so sensitive that you can see it
jumping in sync with the anti-collision strobe.

"Martin Kosina" wrote in message
om...
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.


Hmmm - I thought the ammeter *should* indicate zero when the battery
is fully charged and the electrical load is not changing ? What is the
"normal" indication you are refering to ?



 




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