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Impossible problem

 
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jaybannist(at)cs.com
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PostPosted: Tue Mar 31, 2009 12:41 pm    Post subject: Impossible problem Reply with quote

HELP !!

I there anyone out there willing to dig in hand help me with an impossible problem ?

I have a Zodiac 601XL with a Corvair engine. I have dual fuel pumps and dual ignition coils. The airplane has flown. I designed my electrical system (Scheme 1) thinking that alternators and regulators were mostly bullet proof. Since discovering that was a bad assumption, I decided to power the fuel pumps and coils from the battery bus (Scheme 2). That is the only thing I changed. Now, fuel pump 2 won’t run when I select it with the switch. I tested the fuel pump with a portable battery and it runs. I tested each tab of both switches (Switch analysis). I have continuity between tab 3 of the fuel pump switch and the connector on the fuel pump. I have zero volts on the fuel pump connector. How can that be? And why? Today I changed the wiring to place tabs 2 and 5 of the fuel pump switch to the battery bus and tabs 2 and 5 of the coil switch to the battery bus. Still no joy. I also found that selecting the fuel pump switch either up or down lights the alternator warning light. That obviously shouldn't happen. Surely I am overlooking something, Could I have a bad fuel pump switch? Or what?

Stumped - Jay Bannister
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rampil



Joined: 04 May 2007
Posts: 870

PostPosted: Wed Apr 01, 2009 6:15 am    Post subject: Re: Impossible problem Reply with quote

This may or may not be helpful, but problems like your are most
frequently due to the actual wiring in the airframe being different from
whats on paper. The most profitable thing to do is to voltage and
continuity test to assure conformance to your design.


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nuckolls.bob(at)aeroelect
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PostPosted: Wed Apr 01, 2009 6:39 am    Post subject: Impossible problem Reply with quote

At 03:38 PM 3/31/2009, you wrote:
Quote:
HELP !!

I there anyone out there willing to dig in hand help me with an impossible problem ?

I have a Zodiac 601XL with a Corvair engine. I have dual fuel pumps and dual ignition coils. The airplane has flown. I designed my electrical system (Scheme 1) thinking that alternators and regulators were mostly bullet proof. Since discovering that was a bad assumption, I decided to power the fuel pumps and coils from the battery bus (Scheme 2). That is the only thing I changed. Now, fuel pump 2 won’t run when I select it with the switch. I tested the fuel pump with a portable battery and it runs. I tested each tab of both switches (Switch analysis). I have continuity between tab 3 of the fuel pump switch and the connector on the fuel pump. I have zero volts on the fuel pump connector. How can that be? And why? Today I changed the wiring to place tabs 2 and 5 of the fuel pump switch to the battery bus and tabs 2 and 5 of the coil switch to the battery bus. Still no joy. I also found that selecting the fuel pump switch either up or down lights the alternator warning light. That obviously shouldn't happen. Surely I am overlooking something, Could I have a bad fuel pump switch? Or what?

If it were my airplane, I'd have each of the 4 systems
control through it's own switch and battery bus fuss.
Using -10 switch for BOTH sets of pumps/coils puts a single
point of failure in both pairs of devices. Further,
each device should get it's own fuse at the battery bus.
The 25A fuse and downstream wiring becomes another single
point of failure for two devices. Those are really fat
feeders and fuses . . . how much current do each of these
systems draw?

I'm wondering about the PMR1C rectifier/regulator teamed
with the 20A John Deere PM alternator. The B&C website
speaks to use of the PMR1C with their line of 10A alternators.
Even so, their installation data speaks to a maximum operating
case temperature of 175F and cautions about paying attention
to heating with YOUR installation particulars. See:

http://bandc.biz/PMR1C_Install_DWG.pdf

If I extrapolate their measured temperature values up
to a 20A operating load, you'll be bumping the 175F
limit. Their measured values were probably on the bench
in still air at room temp. Your installation will
no doubt have more air movement but perhaps hotter
environment. It's worth investigating with a measurement
of temperature in flight and at full load.

A useful data point: I'm told that John Deere makes
a PM alternator rectifier-regulator that is compatible
with both their 20 and 35 amp machines. Part No is
AM101406. Pictures of the John Deere products are
seen in

http://home.hiwaay.net/~langford/corvair/dynamo.html

Should you discover that the PMR1C runs a bit too toasty
for comfort, the JD product may offer a plan-b solution.

You have too much "stuff" on your e-bus which prompts
a really fat feeder for the alternate feed path. This
suggests some rethinking on switching of the alternate
feed path feeder to a Z-32 configuration?

Are the position lights LED devices? 2A is light for
feeding incandescent lamps.

Bob . . .


[quote][b]


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nuckolls.bob(at)aeroelect
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PostPosted: Wed Apr 01, 2009 6:42 am    Post subject: Impossible problem Reply with quote

At 03:38 PM 3/31/2009, you wrote:
Quote:
HELP !!

I there anyone out there willing to dig in hand help me with an impossible problem ?

I have a Zodiac 601XL with a Corvair engine. I have dual fuel pumps and dual ignition coils. The airplane has flown. I designed my electrical system (Scheme 1) thinking that alternators and regulators were mostly bullet proof. Since discovering that was a bad assumption, I decided to power the fuel pumps and coils from the battery bus (Scheme 2). That is the only thing I changed. Now, fuel pump 2 won’t run when I select it with the switch. I tested the fuel pump with a portable battery and it runs. I tested each tab of both switches (Switch analysis). I have continuity between tab 3 of the fuel pump switch and the connector on the fuel pump. I have zero volts on the fuel pump connector. How can that be? And why? Today I changed the wiring to place tabs 2 and 5 of the fuel pump switch to the battery bus and tabs 2 and 5 of the coil switch to the battery bus. Still no joy. I also found that selecting the fuel pump switch either up or down lights the alternator warning light. That obviously shouldn't happen. Surely I am overlooking something, Could I have a bad fuel pump switch? Or what?

Okay, assuming no modifications to the architecture
are being considered, let's consider what you've obseved.

There is no connection on your drawing between the fuel pump
selection switch and the alternator warning light. This
suggests a wiring error.

Bob . . . [quote][b]


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jaybannist(at)cs.com
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PostPosted: Wed Apr 01, 2009 9:39 am    Post subject: Impossible problem Reply with quote

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nuckolls.bob(at)aeroelect
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PostPosted: Wed Apr 01, 2009 10:53 am    Post subject: Impossible problem Reply with quote

At 12:37 PM 4/1/2009, you wrote:


Quote:
My MAIN source of concern is that EVERYTHING
worked properly before I made this change; and the
ONLY thing I changed was the source of power to
the coil and fuel pump switches.

Jay

Understand. Without being able to put my
hands on the problem, the most I (or anyone
else) can do is hypothesize about a lot
of things . . . the majority of which will
be irrelevant/wrong.

The laws of physics do not shift their
effects to confound us. There is a specific
reason why you are experiencing the problem
you cited. If you've ever played the board game
Clue, you'll understand that arriving at root
cause is a distillation of facts first to
eliminate those that do not fit into an
explanation of effects and finally identify the
order in which remaining facts explain the
cause for symptoms you've identified.

Snip off the tie wraps, check the wires, follow
the path from bus to appliance with a voltmeter
probe . . . nobody sez it's easy . . . but it
works every time.

Bob . . . [quote][b]


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jaybannist(at)cs.com
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PostPosted: Wed Apr 01, 2009 12:13 pm    Post subject: Impossible problem Reply with quote

Bob,

Thanks. I had about decided that the laws of physics HAD been repealed, or that I was losing my ever-lovin' mind ! Now that you have confirmed that those laws are still intact; I know that my next step is to take all the wiring off those two switches. Then I will positively identify each wire before I reinstall it on the switch. I'll let you know if that fixes the problem.

Thanks again - Jay





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nuckolls.bob(at)aeroelect
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PostPosted: Wed Apr 01, 2009 7:32 pm    Post subject: Impossible problem Reply with quote

At 03:08 PM 4/1/2009, you wrote:
Quote:
Bob,

Thanks. I had about decided that the laws of physics HAD been repealed, or that I was losing my ever-lovin' mind ! Now that you have confirmed that those laws are still intact; I know that my next step is to take all the wiring off those two switches. Then I will positively identify each wire before I reinstall it on the switch. I'll let you know if that fixes the problem.

In particular, you need to identify the "mystery"
connection between pump switches and your alternator
warning light behavior.


Bob . . .

----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------

[quote][b]


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ed(at)muellerartcover.com
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PostPosted: Mon Apr 06, 2009 7:24 am    Post subject: Impossible problem Reply with quote

Jay,

Any luck with the problem? You might consider that maybe the original
wiring isn't correct, only appeared to be. Years ago, I wired a
project (not airplane related) and it worked fine. Couple years later
made a minor alteration and all sorts of strange things started
happening. Turned out the original wiring was incorrect.

Ed
On Apr 1, 2009, at 4:08 PM, jaybannist(at)cs.com wrote:

[quote] Bob,

Thanks. I had about decided that the laws of physics HAD been
repealed, or that I was losing my ever-lovin' mind !  Now that you
have confirmed that those laws are still intact;  I know that my next
step is to take all the wiring off those two switches.  Then I will
positively identify each wire before I reinstall it on the switch. 
I'll let you know if that fixes the problem.

Thanks again - Jay
--


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jaybannist(at)cs.com
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PostPosted: Mon Apr 06, 2009 7:54 am    Post subject: Impossible problem Reply with quote

Ed,

I think you are right. It did work before the change, but that might have just been dumb luck.

My airplane is hangered 40 miles and an hour's drive from my home, right through the middle of Dallas. The upshot is that I don't work on it as often as I want to, or should. My next trip (this week) will be to do a BUNCH of re-wiring. Stay tuned.

Jay





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nuckolls.bob(at)aeroelect
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PostPosted: Mon Apr 06, 2009 10:03 am    Post subject: Impossible problem Reply with quote

At 10:52 AM 4/6/2009, you wrote:
Quote:
Ed,

I think you are right. It did work before the change, but that might have just been dumb luck.

My airplane is hangered 40 miles and an hour's drive from my home, right through the middle of Dallas. The upshot is that I don't work on it as often as I want to, or should. My next trip (this week) will be to do a BUNCH of re-wiring. Stay tuned.


Ed beat me to it. I was about to ask too. We're
all interested in what you find out!



Bob . . .

----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------

[quote][b]


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