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Impossible problem

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jaybannist(at)cs.com
Guest

Posted: Tue Mar 31, 2009 12:41 pm Post subject: Impossible problem

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 wonâ€™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 

   Email message sent from CompuServe - visit us today at http://www.cs.com

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rampil

Joined: 04 May 2007
Posts: 870

Posted: Wed Apr 01, 2009 6:15 am Post subject: Re: Impossible problem

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.

_________________
Ira N224XS

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Apr 01, 2009 6:39 am Post subject: Impossible problem

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 wonâ€™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]

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Apr 01, 2009 6:42 am Post subject: Impossible problem

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 wonâ€™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]

jaybannist(at)cs.com
Guest

Posted: Wed Apr 01, 2009 9:39 am Post subject: Impossible problem

--

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Apr 01, 2009 10:53 am Post subject: Impossible problem

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]

jaybannist(at)cs.com
Guest

Posted: Wed Apr 01, 2009 12:13 pm Post subject: Impossible problem

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

 

   

 

   

 

 --

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Apr 01, 2009 7:32 pm Post subject: Impossible problem

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]

ed(at)muellerartcover.com
Guest

Posted: Mon Apr 06, 2009 7:24 am Post subject: Impossible problem

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

  --

jaybannist(at)cs.com
Guest

Posted: Mon Apr 06, 2009 7:54 am Post subject: Impossible problem

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     

 

   

 

   

 

 --

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Apr 06, 2009 10:03 am Post subject: Impossible problem

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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