The dreaded electrical Gremlins strike again!!

I absolutely HATE electrical issues, and we seem to have another one. My
partner flew from Indianapolis to Dallas (via Oklahoma City) and back
over the weekend. Everything was fine on the way there. On the way back
he started having avionics probems. It started with the VOR needles
twitching and then the 430, fuel totalizer and finally the comms went
inop. He noticed that the landing light would not stay on, like there
was a short somewhere. We had an issue with the landing light wire
shorting out before causing the breaker to not reset. This was fixed
last year.
He was able to make it back to Indianapolis with no issues as long as he
went 2600 rpm and 25 MP. This power MP setting is seems did not cause
the issue to occur. When he throttled back to say 2400 squared the
problem manifested itself again.

So I guess my questions are these:
Could a short circuit in the Landing Light circuit cause anything that I
described?
Has anyone here had an issue like this before? And last but certainly
not least do you have any suggestions?

Thanks!!

Jon Kraus
'79 Mooney 201
4443H @ TYQ

Jon Kraus wrote:
I absolutely HATE electrical issues, and we seem to have another one. My
partner flew from Indianapolis to Dallas (via Oklahoma City) and back
over the weekend. Everything was fine on the way there. On the way back
he started having avionics probems. It started with the VOR needles
twitching and then the 430, fuel totalizer and finally the comms went
inop. He noticed that the landing light would not stay on, like there
was a short somewhere. We had an issue with the landing light wire
shorting out before causing the breaker to not reset. This was fixed
last year.
He was able to make it back to Indianapolis with no issues as long as he
went 2600 rpm and 25 MP. This power MP setting is seems did not cause
the issue to occur. When he throttled back to say 2400 squared the
problem manifested itself again.

So I guess my questions are these:
Could a short circuit in the Landing Light circuit cause anything that I
described?
Has anyone here had an issue like this before? And last but certainly
not least do you have any suggestions?

Maybe a combination of problems.
Heavy electrical load,
+
Alternator not producing enough power. (slipping belt, stuffed
alternator, stuffed regulator),
+
Reduced battery capacity. (age)

My $0.02 is that the problem is somewhere in the alternator/belt region.

MC wrote:
: Maybe a combination of problems.
: Heavy electrical load,
: +
: Alternator not producing enough power. (slipping belt, stuffed
: alternator, stuffed regulator),
: +
: Reduced battery capacity. (age)

: My $0.02 is that the problem is somewhere in the alternator/belt region.

If the alternator/belt stopped producing power, things wouldn't go out until
the battery was dead.

From what you describe, the multisystem failure would tend to indicate
something in common. Possibly a shared breaker (avionics avionics master), but most
likely a single-point, shared ground that's flakey.

Most GA aircraft are a multi-layered hodge-podge of crappy electrical wiring.
In particular, grounds tend to be wherever the last boob to install it had a pre-cut
wire long enough to reach. Having a single-point where everything grounds is a good
thing to eliminate ground loops. Gotta make sure that one point is solid, though.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

wrote:

From what you describe, the multisystem failure would tend to indicate
something in common. Possibly a shared breaker (avionics avionics
master), but most
likely a single-point, shared ground that's flakey.

Most GA aircraft are a multi-layered hodge-podge of crappy electrical
wiring.
In particular, grounds tend to be wherever the last boob to install it
had a pre-cut
wire long enough to reach. Having a single-point where everything
grounds is a good
thing to eliminate ground loops. Gotta make sure that one point is
solid, though.

Concur. Most likely it's not a short, which would pop a breaker. An
intermittent open or high resistance connection would fit the symptoms,
and the ground connections are the places to start looking.

--
Dan
C172RG at BFM

Try a Bad Circuit breaker or a vibration sensitive contact wire to airframe.
Any where wires go through the airframe check the grommets and wiring
for chafing.
Michelle

Jon Kraus wrote:

I absolutely HATE electrical issues, and we seem to have another one.
My partner flew from Indianapolis to Dallas (via Oklahoma City) and
back over the weekend. Everything was fine on the way there. On the
way back he started having avionics probems. It started with the VOR
needles twitching and then the 430, fuel totalizer and finally the
comms went inop. He noticed that the landing light would not stay on,
like there was a short somewhere. We had an issue with the landing
light wire shorting out before causing the breaker to not reset. This
was fixed last year.
He was able to make it back to Indianapolis with no issues as long as
he went 2600 rpm and 25 MP. This power MP setting is seems did not
cause the issue to occur. When he throttled back to say 2400 squared
the problem manifested itself again.

So I guess my questions are these:
Could a short circuit in the Landing Light circuit cause anything that
I described?
Has anyone here had an issue like this before? And last but certainly
not least do you have any suggestions?

Thanks!!

Jon Kraus
'79 Mooney 201
4443H @ TYQ

The alternator and battery are working correctly. This seems to be a
short or a ground issue somewhere.

Thanks!!

JK

MC wrote:

Jon Kraus wrote:

I absolutely HATE electrical issues, and we seem to have another one.
My partner flew from Indianapolis to Dallas (via Oklahoma City) and
back over the weekend. Everything was fine on the way there. On the
way back he started having avionics probems. It started with the VOR
needles twitching and then the 430, fuel totalizer and finally the
comms went inop. He noticed that the landing light would not stay on,
like there was a short somewhere. We had an issue with the landing
light wire shorting out before causing the breaker to not reset. This
was fixed last year.
He was able to make it back to Indianapolis with no issues as long as
he went 2600 rpm and 25 MP. This power MP setting is seems did not
cause the issue to occur. When he throttled back to say 2400 squared
the problem manifested itself again.

So I guess my questions are these:
Could a short circuit in the Landing Light circuit cause anything that
I described?
Has anyone here had an issue like this before? And last but certainly
not least do you have any suggestions?


Maybe a combination of problems.
Heavy electrical load,
+
Alternator not producing enough power. (slipping belt, stuffed
alternator, stuffed regulator),
+
Reduced battery capacity. (age)

My $0.02 is that the problem is somewhere in the alternator/belt region.

The breaker for the landing light is tripping. In a Mooney it is built
in to the switch and the switch will not stay on. I'm thinking that
there is a short somewhere but I don't know why that would cause the
whole avionics bus to go flakey...

Jon Kraus
'79 Mooney 201
4443H @ TYQ

Dan Luke wrote:

wrote:


From what you describe, the multisystem failure would tend to indicate
something in common. Possibly a shared breaker (avionics avionics
master), but most
likely a single-point, shared ground that's flakey.

Most GA aircraft are a multi-layered hodge-podge of crappy electrical
wiring.
In particular, grounds tend to be wherever the last boob to install it
had a pre-cut
wire long enough to reach. Having a single-point where everything
grounds is a good
thing to eliminate ground loops. Gotta make sure that one point is
solid, though.


Concur. Most likely it's not a short, which would pop a breaker. An
intermittent open or high resistance connection would fit the symptoms,
and the ground connections are the places to start looking.

"Jon Kraus" wrote:

The breaker for the landing light is tripping. In a Mooney it is built in
to the switch and the switch will not stay on. I'm thinking that there is a
short somewhere but I don't know why that would cause the whole avionics
bus to go flakey...

Ah, that's different. That might account for some crazy symptoms if it's an
intermittent, high resistence short to ground. It could be pulling the
voltage down enough to make the avionics act up if *they* have a power or
ground connection problem. Perhaps a wire is being pinched somewhere, so
that changing the rpm causes the airframe to flex enough to affect the short.

At least the LL breaker gives you a clue where to start looking. I'd go back
to where the bus feeds the LL circuit and disconnect it, then see what
happens. I'd also still check all the ground and power bus connections,
master switch, etc. for high resistance, as you might have one of those
delightful two-headed gremlins.

Good luck and keep us posted.

--
Dan
C-172RG at BFM

Jon Kraus wrote:
The alternator and battery are working correctly. This seems to be a
short or a ground issue somewhere.

Thanks!!

JK

MC wrote:

Jon Kraus wrote:

I absolutely HATE electrical issues, and we seem to have another one.
My partner flew from Indianapolis to Dallas (via Oklahoma City) and
back over the weekend. Everything was fine on the way there. On the
way back he started having avionics probems. It started with the VOR
needles twitching and then the 430, fuel totalizer and finally the
comms went inop. He noticed that the landing light would not stay on,
like there was a short somewhere. We had an issue with the landing
light wire shorting out before causing the breaker to not reset. This
was fixed last year.
He was able to make it back to Indianapolis with no issues as long as
he went 2600 rpm and 25 MP. This power MP setting is seems did not
cause the issue to occur. When he throttled back to say 2400 squared
the problem manifested itself again.

So I guess my questions are these:
Could a short circuit in the Landing Light circuit cause anything
that I described?
Has anyone here had an issue like this before? And last but certainly
not least do you have any suggestions?



Maybe a combination of problems.
Heavy electrical load,
+
Alternator not producing enough power. (slipping belt, stuffed
alternator, stuffed regulator),
+
Reduced battery capacity. (age)

My $0.02 is that the problem is somewhere in the alternator/belt region.

The post stated that the problem went away when high engine RPM
was used, meaning that the alternator/regulator/battery
combination was not producing enough energy to satisfy the load
at the lower RPMs.

I'm not yet convinced that a ground problem would be overcome
by higher RPMs. (unless it's some wierd resonance effect g)

Hmm, another though has just occured to me.., what if the
battery has a shorted cell ?
That scenario would cause low voltage at the battery and the
regulator will try to send a *lot* of current into the battery
in an effort to get it back to nominal.

The landing light had a wire shorting to ground causing the breaker to
trip. The avionics issue looks like it was a loose wire to the avionics
bus. At least we'll see anyway. Nothing glaringly obvious like the
landing light.

Jon Kraus
'79 Mooney 201
4443H @ TYQ

Dan Luke wrote:

"Jon Kraus" wrote:


The breaker for the landing light is tripping. In a Mooney it is built in
to the switch and the switch will not stay on. I'm thinking that there is a
short somewhere but I don't know why that would cause the whole avionics
bus to go flakey...


Ah, that's different. That might account for some crazy symptoms if it's an
intermittent, high resistence short to ground. It could be pulling the
voltage down enough to make the avionics act up if *they* have a power or
ground connection problem. Perhaps a wire is being pinched somewhere, so
that changing the rpm causes the airframe to flex enough to affect the short.

At least the LL breaker gives you a clue where to start looking. I'd go back
to where the bus feeds the LL circuit and disconnect it, then see what
happens. I'd also still check all the ground and power bus connections,
master switch, etc. for high resistance, as you might have one of those
delightful two-headed gremlins.

Good luck and keep us posted.