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Toggle Switches with Fast-On Tabs **Breaking News**

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rv-9a-online(at)telus.net
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Posted: Tue Sep 16, 2008 9:57 am Post subject: Toggle Switches with Fast-On Tabs **Breaking News**

Here's  some breaking news for those following the burnt-switch  thread:

  

 I am  receipt of a photo from another builder that shows three switches with burnt  fast-on tabs!  He's identified that two of the switches are the Wig-Wag  switch and the Strobe switch.  Not sure what the third one is for.  I  am getting more information and will post it here, including the indentification  of the switches and the brands.

  

 Compare this new photo:  http://www.vx-aviation.com/rv-9a/photos/Electrical/PH_Switches.JPG

  

 With  the photo from my aircraft:  http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0935_2.JPG

  

 My  investigation shows no burned terminals on my Wig-Wag, Landing or Taxi switches,  although they did get warm.  I do have inrush current limiters on the  lighting circuits.  My Strobe switch (photo) was toasted, literally, as  shown in the second photo.

  

 What  are the commonalities here?  Both are from RV-9As but that's  irrelevant.  Both aircraft have problems with both the Strobe and Wig-Wag  switches (and potentially Landing and Taxi circuits as well).  Have yet to  identify the switch manufacturers, but evidence is leaning towards  brand-independence.

  

 Stay  tuned.

  

 Vern

  

  

   [quote][b]

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rv-9a-online(at)telus.net
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Posted: Tue Sep 16, 2008 10:29 am Post subject: Toggle Switches with Fast-On Tabs **Breaking News**

One  correction, there are only 2 switches affected in the photo, the third has a  black tie-wrap on it!  The two circuits that show distress (left  to right) are the Wig-Wag  and Strobe switches.

 I have  confirmed that the Strobe switch is made by Carling, but the Wig-Wag brand has  not been confirmed.

  

 Vern

 [quote]   

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Neal.George(at)hurlburt.a
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Posted: Tue Sep 16, 2008 12:02 pm Post subject: Toggle Switches with Fast-On Tabs **Breaking News**

Vern - 



I'm betting on sub-standard crimps in high-current circuits.  As in not

enough wire in the tube to make a proper crimp.  For the sake of

argument, let's call that a "light" crimp.  A light crimp may withstand

a tug-test, but then begin to loosen up under the vibration and heat

cycles of normal operation.  Heat cycles then accelerate deterioration

of the joint.  



Neal

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rv-9a-online(at)telus.net
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Posted: Tue Sep 16, 2008 12:53 pm Post subject: Toggle Switches with Fast-On Tabs **Breaking News**

I've got some crimps into Bob for F/A, so we can test your theory.  It's a

bit worrisome, however, that (at least) three persons have had similar

failures on their strobe switches, and two on their lamp switches.  



The other photo I provided is from a builder 3000 miles away, using the same

fast-ons and presumably the same crimper.



Vern



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rv-9a-online(at)telus.net
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Posted: Tue Sep 16, 2008 12:56 pm Post subject: Toggle Switches with Fast-On Tabs **Breaking News**

More  information from the new photo (friend's airplane).  The Wig-Wag switch  that is failing is from: http://www.apem.com/pdf/600H-600NH.pdf.  It is a 644H.

 The wig-wag circuit is flashing an MR16 50W lamp.  The  HID landing light switch looks fine.  Strobe is a Carling  switch.

  

 More data.... maybe not more information,  yet!

  

 Vern

 [quote]   

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rv-9a-online(at)telus.net
Guest

Posted: Wed Sep 17, 2008 7:50 pm Post subject: Toggle Switches with Fast-On Tabs **Breaking News**

OK,  here's where I'm heading:  Strobe switches are failing.  We now have 5  confirmed failures (I've had 2, Bob Nuckolls has done a failure analysis on  another, plus three more that I have been advised about recently).  In  addition, we've had wig-wag and landing/taxi switch failures  reported.

  

 The  most recent information I have from the new case documented in the previous  message is that yes, indeed, the switch rivets are loose.  It looks  like a common contributing factor.

  

 Since  my replacement switches work fine, but only have a couple of hours of flight  time on them, it's tough to tell if we have a problem with certain  manufacturers' switches, or an application problem.  At this point, I'm  betting that we have an application problem due to the high inrush currents that  landing/taxi lamps and strobe supplies exhibit.

  

 Bob,  based on my personal experience and the evidence provided by others, I think it  would be a good idea to use high-inrush automotive relays for these circuits,  controlled by low-cost switches.  Since landing and taxi lights are often  wig-wagged, it would be possible to replace the wig-wag flasher with a  configuration that only uses relays to handle the high currents in all three  modes (wig-wag, taxi, landing).  The Strobe circuit would be a simple SPST  relay.

  

 I know  you haven't received my bag-o-bits with the failed switch components and crimps  yet so I may be jumping the gun.  Nevertheless, there are enough burning  switches and terminals out there where we have a potential safety problem that  needs to be addressed.  Relays may be a band-aid to cover up cheap switch  design, but they are designed for this purpose and are very  reliable.

  

 Thanks,

 Vern

  

  

 

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