The dreaded electrical Gremlins strike again!!

[Jon Kraus]

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

[MC]

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.

[[email protected]]

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 *
************************************************** ***********************

[Dan Luke]

> 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

[Michelle P]

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
>

[Jon Kraus]

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.

[Jon Kraus]

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.
>

[Dan Luke]

"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

[MC]

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.

[Jon Kraus]

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.
>

[Jon Kraus]

My partner was thinking that the problem went away when the engine
smoothed out at the highter RPM. I asked him if he pulled back the power
on the way back from Oklahoma to see if he could get the avionics to
crap out again and he said "Hell no" I just wanted to get back. Can't
say that I blame him. :-)

Jon Kraus
'79 Mooney 201
4443H @ TYQ


>
> 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.