Today's Message Index:
----------------------
1. 06:17 AM - Re: Switch problem ***MAJOR UPDATE*** (Robert L. Nuckolls, III)
2. 06:17 AM - Re: Switch problem ***MAJOR UPDATE*** (Robert L. Nuckolls, III)
3. 09:10 AM - Re: Switch problem ***MAJOR UPDATE*** (Vernon Little)
4. 10:03 AM - Re: Switch problem ***MAJOR UPDATE*** (David E. Nelson)
5. 10:19 AM - B+C Alternator problem (rocket2man)
6. 11:12 AM - Re: Switch problem ***MAJOR UPDATE*** (Richard Tasker)
7. 11:42 AM - Re: Switch problem ***MAJOR UPDATE*** (Vernon Little)
8. 11:49 AM - Re: Switch problem ***MAJOR UPDATE*** (Vernon Little)
9. 02:18 PM - Re: Switch problem ***MAJOR UPDATE*** (Robert L. Nuckolls, III)
10. 05:35 PM - Re: Switch problem ***MAJOR UPDATE*** (Vernon Little)
Message 1
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Subject: | Re: Switch problem ***MAJOR UPDATE*** |
At 07:20 PM 9/10/2008 -0600, you wrote:
>
>Hi Vern,
>
>Check the crimps on your faston connectors. If the crimps are getting
>hot they could be conducting heat into the switch tabs. The simplest
>way to check would be to make a male faston jumper and replace one of
>the switches that is getting hot, then turn on the master.
>
>It might be a bad batch of switches, but it would be worth checking the
>crimps before pulling all of them out.
>
>Bob W.
An excellent suggestion for covering all the bases!
Carling has been in this business for a very long time
and their total output of switches is probably 1000+ times
greater than what goes into airplanes. I can see
the occasional 'batch' problems with process but
Vern's experience is mystifying.
The simple-ideas of physics that drive conditions
he's observed are solid and irrefutable. We just need
to carefully sift the sand. If anyone else has a
suggestion for the pursuit of knowledge, it's time
to bring it up.
Vern, what fast-on terminals did you use and which
tool was used to apply them? Save all the pieces
and parts that are replaced. They can yield important
information in the 'autopsy'.
Bob . . .
Message 2
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Subject: | Switch problem ***MAJOR UPDATE*** |
At 07:26 PM 9/10/2008 -0700, you wrote:
><rv-9a-online@telus.net>
>
>I will check this for sure, but the evidence is contrary. If it was the
>crimps that were the source, they should all be discolored. In addition, I
>felt the terminals when operating to see if they were loose. They were not,
>and they were not as hot as the switch.
>
>I pulled apart one of the failed switches (from one of the two that failed
>in 2006) and it was damaged, similar to Bob's failure analysis on his
>website.
>
>The terminals are the Avikrimp type and attached using a proper ratcheting
>crimp tool.
>
>I've ordered a batch of Honeywell Micro Switch switches as replacements. I
>will pull all of the offending Carling switches and redo the burnt fastons
>on the Strobe supply switch (for the second time). I will probably
>sacrifice another one of the Carling switches to failure analysis gods to
>see if the internals are fried like the first one.
>
>Fortunately, the switches run in a row along the bottom of my panel and are
>easy to replace. See
>http://www.vx-aviation.com/rv-9a/photos/Electrical/115_1542_1.jpg. It
>should only take me an hour to do the major offenders and get back in the
>air. Right now, I've grounded my a/c due to this problem.
>
>Stay tuned.
Sounds like a plan.
Bob . . .
Message 3
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Subject: | Switch problem ***MAJOR UPDATE*** |
OK, here's the first data from my switch failure:
- The following is a drawing of my landing/taxi/wig-wag circuit. Please
note that the Strobe circuit is straightforward, with a 3-1 switch connected
to the main bus. All four of these switches are getting hot: TAXI,
LANDING, FLASH and STROBE.
http://www.vx-aviation.com/rv-9a/photos/Electrical/wigwag.jpg
- The following are similar photos of the failed switches, in-situ. Left to
right: FLASH switch (hot), STROBE switch (burned fast-ons), NAV switch (no
problems to date)
http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0936_1.JPG
http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0935_2.JPG
The only discernable problem from these photos is the burned fast-ons, but
the switch was dangerously hot to touch in operation. The FLASH switch
(just visable on the left) gets hot (but not as hot) as well, but no burned
terminals.
My order for new switches arives today (gotta love Digikey in Canada:
ordered at 4:45 pm yesterday, will have them here by noon today... For $8.00
shipping). I will pull & replace the old switches, and replace the burned
fast-ons. I'll keep them for F/A.
All of my terminals were purchased either from Steinair or Digikey-- all are
Molex Avikrimp: http://www.molex.com/pdm_docs/sd/190020002_sd.pdf
The crimper was also purchased from Steinair and is similar to:
http://www.steinair.com/images/store/panels/sat001.jpg or
http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?account=X358218;sear
ch=RCT-1;search=PIDG%20Style%20Crimp%20Tool;limit=product;v=2.0
Stay tuned, I will post more of my findings as I rework my a/c.
Vern
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: September 11, 2008 6:16 AM
Subject: Re: AeroElectric-List: Switch problem ***MAJOR UPDATE***
--> <nuckolls.bob@cox.net>
At 07:20 PM 9/10/2008 -0600, you wrote:
>
>Hi Vern,
>
>Check the crimps on your faston connectors. If the crimps are getting
>hot they could be conducting heat into the switch tabs. The simplest
>way to check would be to make a male faston jumper and replace one of
>the switches that is getting hot, then turn on the master.
>
>It might be a bad batch of switches, but it would be worth checking the
>crimps before pulling all of them out.
>
>Bob W.
An excellent suggestion for covering all the bases!
Carling has been in this business for a very long time
and their total output of switches is probably 1000+ times
greater than what goes into airplanes. I can see
the occasional 'batch' problems with process but
Vern's experience is mystifying.
The simple-ideas of physics that drive conditions
he's observed are solid and irrefutable. We just need
to carefully sift the sand. If anyone else has a
suggestion for the pursuit of knowledge, it's time
to bring it up.
Vern, what fast-on terminals did you use and which
tool was used to apply them? Save all the pieces
and parts that are replaced. They can yield important
information in the 'autopsy'.
Bob . . .
Message 4
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Subject: | Switch problem ***MAJOR UPDATE*** |
Hi Vernon,
I noticed something odd in
http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0935_2.JPG
It's kinda hard to see the fast-on in the background, so I'm not sure.
Are both fast-on's discolored or just the one in the foreground? Also,
there appears to be some discoloration of the wire itself for the fast-on
in the background. Is this just a shadow?
The fast-on tabs and their associated rivets don't appear to be
discolored.
Just going on the pictures, seems to me that the crimp just is not up to
the task. I'll be interested in hearing what Bob sees.
Thanks for sharing,
/\/elson
~~ Lately my memory seems to be like a steel trap .... without any spring. ~~
On Thu, 11 Sep 2008, Vernon Little wrote:
>
> OK, here's the first data from my switch failure:
>
> - The following is a drawing of my landing/taxi/wig-wag circuit. Please
> note that the Strobe circuit is straightforward, with a 3-1 switch connected
> to the main bus. All four of these switches are getting hot: TAXI,
> LANDING, FLASH and STROBE.
> http://www.vx-aviation.com/rv-9a/photos/Electrical/wigwag.jpg
>
> - The following are similar photos of the failed switches, in-situ. Left to
> right: FLASH switch (hot), STROBE switch (burned fast-ons), NAV switch (no
> problems to date)
>
> http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0936_1.JPG
>
> The only discernable problem from these photos is the burned fast-ons, but
> the switch was dangerously hot to touch in operation. The FLASH switch
> (just visable on the left) gets hot (but not as hot) as well, but no burned
> terminals.
>
> My order for new switches arives today (gotta love Digikey in Canada:
> ordered at 4:45 pm yesterday, will have them here by noon today... For $8.00
> shipping). I will pull & replace the old switches, and replace the burned
> fast-ons. I'll keep them for F/A.
>
> All of my terminals were purchased either from Steinair or Digikey-- all are
> Molex Avikrimp: http://www.molex.com/pdm_docs/sd/190020002_sd.pdf
> The crimper was also purchased from Steinair and is similar to:
> http://www.steinair.com/images/store/panels/sat001.jpg or
> http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?account=X358218;sear
> ch=RCT-1;search=PIDG%20Style%20Crimp%20Tool;limit=product;v=2.0
>
> Stay tuned, I will post more of my findings as I rework my a/c.
>
> Vern
>
>
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
> Nuckolls, III
> Sent: September 11, 2008 6:16 AM
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Switch problem ***MAJOR UPDATE***
>
>
> --> <nuckolls.bob@cox.net>
>
> At 07:20 PM 9/10/2008 -0600, you wrote:
>>
>> Hi Vern,
>>
>> Check the crimps on your faston connectors. If the crimps are getting
>> hot they could be conducting heat into the switch tabs. The simplest
>> way to check would be to make a male faston jumper and replace one of
>> the switches that is getting hot, then turn on the master.
>>
>> It might be a bad batch of switches, but it would be worth checking the
>> crimps before pulling all of them out.
>>
>> Bob W.
>
> An excellent suggestion for covering all the bases!
> Carling has been in this business for a very long time
> and their total output of switches is probably 1000+ times
> greater than what goes into airplanes. I can see
> the occasional 'batch' problems with process but
> Vern's experience is mystifying.
>
> The simple-ideas of physics that drive conditions
> he's observed are solid and irrefutable. We just need
> to carefully sift the sand. If anyone else has a
> suggestion for the pursuit of knowledge, it's time
> to bring it up.
>
> Vern, what fast-on terminals did you use and which
> tool was used to apply them? Save all the pieces
> and parts that are replaced. They can yield important
> information in the 'autopsy'.
>
> Bob . . .
>
>
Message 5
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Subject: | B+C Alternator problem |
Time: 09:44:38 AM PST US
From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
Subject: Re: AeroElectric-List: B+C alternator problem
> >
> > Call B&C at 316-283-8000 and see if they're interested
> > in updating your LR-3 with respect to noise immunity.
> > If push comes to shove, I can modify it for you but
> > let's see what they say first.
> >
> > Bob . . .
> >
> >Bob -
> >Talked to Bill at B+C this afternoon and he wasn't too convinced the
LR-3B
> >needed much of an upgrade. He says there is a LR-3C being built now
and I
> >get the idea it has some transient type improvements built in. His
> >suggestion was to monitor the low voltage light to see under which
> >conditions it comes on. I don't think I can get it to trip when I
> >want. I am suspecting it might not be a consistent cause i.e. the
dreaded
> >intermittent type of thing. But, I now know enough about the
location of
> >components in my particular system to troubleshoot if I knew where to
> >start. The only thing I have done is put a 20 amp fuse in the field
> >location. I haven't flown it yet this way. JBB
This tends to confirm my suspicion that B&C has
probably not replaced departed technical staff that
used to support this and other products . . .
It's true that the "C" version was crafted to offset the
effects of an extra-ordinary (outside the Mil-Std-704
envelope) noise situation on the G36 Bonanza. It's
also true that your particular installation may be
generating some un-anticipated stress that upsets
the ov protection.
I should point out here . . . AGAIN . . . that this
situation is not unique to the so-called "crowbar"
shutdown philosophy. It's a situation driven by the
dynamics of circuitry that watches for an ov condition
and makes a Let-Run/Shut-Down decision. It's a system
design and integration problem that must be solved
irrespective of the designer's choice for shut-down
philosophy. I.e, anyone's OV protection scheme can
be similarly "spoofed" into an unnecessary shutdown
event.
My sense is that B&C is hopeful of keeping this prolem
out of their shops . . . so let's do this.
The upstream field supply protection should be a 5A
breaker. If there's a "fusible" function upstream
of the breaker, make it a 24AWG fusible link. Let's
get the unit-fuse out of the system. The breaker
should be mounted within reach of the pilot.
Let's do some flying and see if you can identify
the antagonist condition. By the way, I'm assuming
you DO have a single point ground behind the panel
for all the electro-whizzies? Let's conduct some
experiments to see if the noise source can
be deduced.
If push comes to shove, you can mail me your regulator
and I'll modify it here. I think I recall all the things
we did to them . . . but it's been 7-10 years ago.
Bob . . .
Bob -
Back in town. I will replace the 15 amp fuse with a 5 amp C/B
accessible to the pilot.
I am also making a detailed digram of the wiring to make sure there
aren't any rogue units in there somewhere. I am not sure if there is
any other fusible link in the wiring path but the B+C LR-3B is
accessible for wire tracing so I will make sure what's there.
I'll fly the airplane as you suggested and see if I can make it trip the
C/B.
JBB
Message 6
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Subject: | Re: Switch problem ***MAJOR UPDATE*** |
I noticed the same thing. Have you ever done a pull test with some of
the terminals crimped with this tool? The depth of the crimp looks
somewhat shallow compared to the ones on my plane, but it could be an
illusion from the photo or maybe the plastic could have "relaxed" due to
the heat.
Dick Tasker
David E. Nelson wrote:
> <david.nelson@pobox.com>
>
>
> Hi Vernon,
>
> I noticed something odd in
>
> http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0935_2.JPG
>
> It's kinda hard to see the fast-on in the background, so I'm not sure.
> Are both fast-on's discolored or just the one in the foreground?
> Also, there appears to be some discoloration of the wire itself for
> the fast-on in the background. Is this just a shadow?
>
> The fast-on tabs and their associated rivets don't appear to be
> discolored.
>
> Just going on the pictures, seems to me that the crimp just is not up
> to the task. I'll be interested in hearing what Bob sees.
>
> Thanks for sharing,
>
> /\/elson
>
>
> ~~ Lately my memory seems to be like a steel trap .... without any
> spring. ~~
>
> On Thu, 11 Sep 2008, Vernon Little wrote:
>
>> <rv-9a-online@telus.net>
>>
>> OK, here's the first data from my switch failure:
>>
>> - The following is a drawing of my landing/taxi/wig-wag circuit. Please
>> note that the Strobe circuit is straightforward, with a 3-1 switch
>> connected
>> to the main bus. All four of these switches are getting hot: TAXI,
>> LANDING, FLASH and STROBE.
>> http://www.vx-aviation.com/rv-9a/photos/Electrical/wigwag.jpg
>>
>> - The following are similar photos of the failed switches, in-situ.
>> Left to
>> right: FLASH switch (hot), STROBE switch (burned fast-ons), NAV
>> switch (no
>> problems to date)
>>
>> http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0936_1.JPG
>>
>> The only discernable problem from these photos is the burned
>> fast-ons, but
>> the switch was dangerously hot to touch in operation. The FLASH switch
>> (just visable on the left) gets hot (but not as hot) as well, but no
>> burned
>> terminals.
>>
>> My order for new switches arives today (gotta love Digikey in Canada:
>> ordered at 4:45 pm yesterday, will have them here by noon today...
>> For $8.00
>> shipping). I will pull & replace the old switches, and replace the
>> burned
>> fast-ons. I'll keep them for F/A.
>>
>> All of my terminals were purchased either from Steinair or Digikey--
>> all are
>> Molex Avikrimp: http://www.molex.com/pdm_docs/sd/190020002_sd.pdf
>> The crimper was also purchased from Steinair and is similar to:
>> http://www.steinair.com/images/store/panels/sat001.jpg or
>> http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?account=X358218;sear
>>
>> ch=RCT-1;search=PIDG%20Style%20Crimp%20Tool;limit=product;v=2.0
>>
>> Stay tuned, I will post more of my findings as I rework my a/c.
>>
>> Vern
>>
>>
>>
>> -----Original Message-----
>> From: owner-aeroelectric-list-server@matronics.com
>> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
>> Robert L.
>> Nuckolls, III
>> Sent: September 11, 2008 6:16 AM
>> To: aeroelectric-list@matronics.com
>> Subject: Re: AeroElectric-List: Switch problem ***MAJOR UPDATE***
>>
>>
>>
>> --> <nuckolls.bob@cox.net>
>>
>> At 07:20 PM 9/10/2008 -0600, you wrote:
>>>
>>> Hi Vern,
>>>
>>> Check the crimps on your faston connectors. If the crimps are getting
>>> hot they could be conducting heat into the switch tabs. The simplest
>>> way to check would be to make a male faston jumper and replace one of
>>> the switches that is getting hot, then turn on the master.
>>>
>>> It might be a bad batch of switches, but it would be worth checking the
>>> crimps before pulling all of them out.
>>>
>>> Bob W.
>>
>> An excellent suggestion for covering all the bases!
>> Carling has been in this business for a very long time
>> and their total output of switches is probably 1000+ times
>> greater than what goes into airplanes. I can see
>> the occasional 'batch' problems with process but
>> Vern's experience is mystifying.
>>
>> The simple-ideas of physics that drive conditions
>> he's observed are solid and irrefutable. We just need
>> to carefully sift the sand. If anyone else has a
>> suggestion for the pursuit of knowledge, it's time
>> to bring it up.
>>
>> Vern, what fast-on terminals did you use and which
>> tool was used to apply them? Save all the pieces
>> and parts that are replaced. They can yield important
>> information in the 'autopsy'.
>>
>> Bob . . .
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>
Message 7
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Subject: | Switch problem ***MAJOR UPDATE*** |
Hi Nelson. Both tabs are discolored, although the one in the foreground is
worse. There is some discoloration on the wire you mentioned. I think that
this is from the adhesive residue of the wire label that dried up and fell
off due to the heat. I will inspect more closely when I replace the
switches.
As for the crimp, I'll save the tab and stub wire for F/A.
You are right about the tabs and rivets, although the first failure I had in
2006 had discoloration. The 2006 failure also had a tripping CB, so it may
have been a failure similar to the one Bob documented on his web site.
The new Micro Switch switches arrived at 9:45 this AM (17 hour delivery from
Digikey!)have a slightly higher rating (20A/125V vs 15A/125V) and the
construction seems to be more refined, with solid rivets vs hollow rivets
and a closer tolerance on the moulding to prevent the tabs from rotating. I
don't have any knowledge of the internal construction, though. They are a
lot more expensive, so hopefully price and quality are positively
correlated.
Vern
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of David E.
Nelson
Sent: September 11, 2008 10:02 AM
Subject: RE: AeroElectric-List: Switch problem ***MAJOR UPDATE***
--> <david.nelson@pobox.com>
Hi Vernon,
I noticed something odd in
http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0935_2.JPG
It's kinda hard to see the fast-on in the background, so I'm not sure.
Are both fast-on's discolored or just the one in the foreground? Also,
there appears to be some discoloration of the wire itself for the fast-on
in the background. Is this just a shadow?
The fast-on tabs and their associated rivets don't appear to be
discolored.
Just going on the pictures, seems to me that the crimp just is not up to
the task. I'll be interested in hearing what Bob sees.
Thanks for sharing,
/\/elson
~~ Lately my memory seems to be like a steel trap .... without any spring.
~~
On Thu, 11 Sep 2008, Vernon Little wrote:
> --> <rv-9a-online@telus.net>
>
> OK, here's the first data from my switch failure:
>
> - The following is a drawing of my landing/taxi/wig-wag circuit.
> Please note that the Strobe circuit is straightforward, with a 3-1
> switch connected to the main bus. All four of these switches are
> getting hot: TAXI, LANDING, FLASH and STROBE.
> http://www.vx-aviation.com/rv-9a/photos/Electrical/wigwag.jpg
>
> - The following are similar photos of the failed switches, in-situ.
> Left to
> right: FLASH switch (hot), STROBE switch (burned fast-ons), NAV switch
(no
> problems to date)
>
> http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0936_1.JPG
>
> The only discernable problem from these photos is the burned fast-ons,
> but the switch was dangerously hot to touch in operation. The FLASH
> switch (just visable on the left) gets hot (but not as hot) as well,
> but no burned terminals.
>
> My order for new switches arives today (gotta love Digikey in Canada:
> ordered at 4:45 pm yesterday, will have them here by noon today... For
$8.00
> shipping). I will pull & replace the old switches, and replace the
burned
> fast-ons. I'll keep them for F/A.
>
> All of my terminals were purchased either from Steinair or Digikey--
> all are Molex Avikrimp:
> http://www.molex.com/pdm_docs/sd/190020002_sd.pdf
> The crimper was also purchased from Steinair and is similar to:
> http://www.steinair.com/images/store/panels/sat001.jpg or
>
http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?account=X358218;sear
> ch=RCT-1;search=PIDG%20Style%20Crimp%20Tool;limit=product;v=2.0
>
> Stay tuned, I will post more of my findings as I rework my a/c.
>
> Vern
>
>
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
> Robert L. Nuckolls, III
> Sent: September 11, 2008 6:16 AM
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Switch problem ***MAJOR UPDATE***
>
>
> --> <nuckolls.bob@cox.net>
>
> At 07:20 PM 9/10/2008 -0600, you wrote:
>> --> <bob@bob-white.com>
>>
>> Hi Vern,
>>
>> Check the crimps on your faston connectors. If the crimps are
>> getting hot they could be conducting heat into the switch tabs. The
>> simplest way to check would be to make a male faston jumper and
>> replace one of the switches that is getting hot, then turn on the
>> master.
>>
>> It might be a bad batch of switches, but it would be worth checking
>> the crimps before pulling all of them out.
>>
>> Bob W.
>
> An excellent suggestion for covering all the bases!
> Carling has been in this business for a very long time
> and their total output of switches is probably 1000+ times
> greater than what goes into airplanes. I can see
> the occasional 'batch' problems with process but
> Vern's experience is mystifying.
>
> The simple-ideas of physics that drive conditions
> he's observed are solid and irrefutable. We just need
> to carefully sift the sand. If anyone else has a
> suggestion for the pursuit of knowledge, it's time
> to bring it up.
>
> Vern, what fast-on terminals did you use and which
> tool was used to apply them? Save all the pieces
> and parts that are replaced. They can yield important
> information in the 'autopsy'.
>
> Bob . . .
>
>
Message 8
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Subject: | Switch problem ***MAJOR UPDATE*** |
Hi Dick. I do a pull test on every crimp, although this is not a direct
measurement of termination resistance.
One thing for sure, it's readily apparent why we don't use PVC insulated
terminals... They insulation would have melted.
As for the depth of the crimp, it's tough to tell how the metal ferrule has
crimped by looking through the insulation. The insulation is very tough and
tends to relax a bit after crimping.
I hope to get to the hangar today, so I'll provide an update later tonight
or tomorrow.
Vern
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Richard
Tasker
Sent: September 11, 2008 11:10 AM
Subject: Re: AeroElectric-List: Switch problem ***MAJOR UPDATE***
--> <retasker@optonline.net>
I noticed the same thing. Have you ever done a pull test with some of
the terminals crimped with this tool? The depth of the crimp looks
somewhat shallow compared to the ones on my plane, but it could be an
illusion from the photo or maybe the plastic could have "relaxed" due to
the heat.
Dick Tasker
David E. Nelson wrote:
> <david.nelson@pobox.com>
>
>
> Hi Vernon,
>
> I noticed something odd in
>
> http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0935_2.JPG
>
> It's kinda hard to see the fast-on in the background, so I'm not sure.
> Are both fast-on's discolored or just the one in the foreground?
> Also, there appears to be some discoloration of the wire itself for
> the fast-on in the background. Is this just a shadow?
>
> The fast-on tabs and their associated rivets don't appear to be
> discolored.
>
> Just going on the pictures, seems to me that the crimp just is not up
> to the task. I'll be interested in hearing what Bob sees.
>
> Thanks for sharing,
>
> /\/elson
>
>
> ~~ Lately my memory seems to be like a steel trap .... without any
> spring. ~~
>
> On Thu, 11 Sep 2008, Vernon Little wrote:
>
>> <rv-9a-online@telus.net>
>>
>> OK, here's the first data from my switch failure:
>>
>> - The following is a drawing of my landing/taxi/wig-wag circuit.
>> Please note that the Strobe circuit is straightforward, with a 3-1
>> switch connected to the main bus. All four of these switches are
>> getting hot: TAXI, LANDING, FLASH and STROBE.
>> http://www.vx-aviation.com/rv-9a/photos/Electrical/wigwag.jpg
>>
>> - The following are similar photos of the failed switches, in-situ.
>> Left to
>> right: FLASH switch (hot), STROBE switch (burned fast-ons), NAV
>> switch (no
>> problems to date)
>>
>> http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0936_1.JPG
>>
>> The only discernable problem from these photos is the burned
>> fast-ons, but
>> the switch was dangerously hot to touch in operation. The FLASH switch
>> (just visable on the left) gets hot (but not as hot) as well, but no
>> burned
>> terminals.
>>
>> My order for new switches arives today (gotta love Digikey in Canada:
>> ordered at 4:45 pm yesterday, will have them here by noon today...
>> For $8.00
>> shipping). I will pull & replace the old switches, and replace the
>> burned
>> fast-ons. I'll keep them for F/A.
>>
>> All of my terminals were purchased either from Steinair or Digikey--
>> all are
>> Molex Avikrimp: http://www.molex.com/pdm_docs/sd/190020002_sd.pdf
>> The crimper was also purchased from Steinair and is similar to:
>> http://www.steinair.com/images/store/panels/sat001.jpg or
>>
http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?account=X358218;sear
>>
>> ch=RCT-1;search=PIDG%20Style%20Crimp%20Tool;limit=product;v=2.0
>>
>> Stay tuned, I will post more of my findings as I rework my a/c.
>>
>> Vern
>>
>>
>>
>> -----Original Message-----
>> From: owner-aeroelectric-list-server@matronics.com
>> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
>> Robert L.
>> Nuckolls, III
>> Sent: September 11, 2008 6:16 AM
>> To: aeroelectric-list@matronics.com
>> Subject: Re: AeroElectric-List: Switch problem ***MAJOR UPDATE***
>>
>>
>>
>> --> <nuckolls.bob@cox.net>
>>
>> At 07:20 PM 9/10/2008 -0600, you wrote:
>>> --> <bob@bob-white.com>
>>>
>>> Hi Vern,
>>>
>>> Check the crimps on your faston connectors. If the crimps are
>>> getting hot they could be conducting heat into the switch tabs. The
>>> simplest way to check would be to make a male faston jumper and
>>> replace one of the switches that is getting hot, then turn on the
>>> master.
>>>
>>> It might be a bad batch of switches, but it would be worth checking
>>> the crimps before pulling all of them out.
>>>
>>> Bob W.
>>
>> An excellent suggestion for covering all the bases!
>> Carling has been in this business for a very long time
>> and their total output of switches is probably 1000+ times
>> greater than what goes into airplanes. I can see
>> the occasional 'batch' problems with process but
>> Vern's experience is mystifying.
>>
>> The simple-ideas of physics that drive conditions
>> he's observed are solid and irrefutable. We just need
>> to carefully sift the sand. If anyone else has a
>> suggestion for the pursuit of knowledge, it's time
>> to bring it up.
>>
>> Vern, what fast-on terminals did you use and which
>> tool was used to apply them? Save all the pieces
>> and parts that are replaced. They can yield important
>> information in the 'autopsy'.
>>
>> Bob . . .
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>
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Subject: | Switch problem ***MAJOR UPDATE*** |
The photo at:
http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0935_2.JPG
shows very localized discoloration of the terminal
insulator. There's a large temperature gradient when
you consider heat flow path from a high-resistance
contact within the switch out through riveted joint,
terminal tab, fast-on socket and to the plastic insulator.
I'm not seeing any signs of heating of the switch-tab
or the fast-on socket. The fact you ARE seeing so much
effects of heating due to poor contact in so many places
places the application tool in question. See the wire-
grip photos at:
http://www.aeroelectric.com/articles/CrimpTools/crimptools.html
This is a critical issue for mating tools-to-terminals-to-wire.
If you would care to send me some exemplar terminals installed
on wires, I'd be pleased to get a look at the microscopic details
of the wire grip.
Bob . . .
Message 10
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Subject: | Switch problem ***MAJOR UPDATE*** |
Hi Bob. Thanks for your comments. See my reply, plus my new findings of
today:
>
> The photo at:
>
> http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0935_2.JPG
>
> shows very localized discoloration of the terminal
> insulator. There's a large temperature gradient when
> you consider heat flow path from a high-resistance
> contact within the switch out through riveted joint,
> terminal tab, fast-on socket and to the plastic insulator.
>
> I'm not seeing any signs of heating of the switch-tab
> or the fast-on socket. The fact you ARE seeing so much
> effects of heating due to poor contact in so many places
> places the application tool in question. See the wire-
> grip photos at:
>
> http://www.aeroelectric.com/articles/CrimpTools/crimptools.html
>
> This is a critical issue for mating tools-to-terminals-to-wire.
>
> If you would care to send me some exemplar terminals installed
> on wires, I'd be pleased to get a look at the microscopic details
> of the wire grip.
>
> Bob . . .
>
After removing all of my SPDT switches and replacing them, I did, indeed
find some discoloration of two terminals on the Strobe switch. Since the
Landing light was getting a bit warm as well, I looked at it-- no
discoloration. I opened up the switches and looked at the rocker bars, see
photo: http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0955_1.JPG
and http://www.vx-aviation.com/rv-9a/photos/Electrical/IMG_0956_2.JPG.
In both cases, the landing light rocker is on the left, and the strobe
rocker on the right. It's not apparent from the photos, but the strobe
rocker has discolored. The second photo shows that the lubricating grease
has carbonized due to internal heating. Also, the center rivet on the
switch was very loose, leading to a significant voltage drop across the
switch of 2 volts when measure in-situ with strobes operating (and it got
very hot!).
Both rockers were relatively flat, with only slight curls to them.
So it's safe to conclude that both the strobe switch and the related
fast-ons have heat damage. The landing light switch was in much better
condition, with no fast-on discoloration or obvious internal problems.
What is causing these recurrent problems? One theory is bad crimps, the
other is bad switches. Maybe one is causing the other. If a crimp is
faulty, and causes heating of the terminal, perhaps this triggers problems
in the switches, which then heat up as well. Or maybe it's the other way
around. To test this theory, I replaced the strobe switch and left the
discolored fast-ons in place: No problem, switch and terminals remained
cool, and voltage drop across the switch was unmeasurable. Seems to
indicate a switch problem, but not conclusive. I later cut off the
discolored fast-ons and I'l be mailing them to Bob along with some test
crimps from my crimper.
BTW, I tested all of the replacement switches in my A/C. No heat problems
to report. Time will tell, of course.
I'd sure like to hear from others-- run out and feel your switches and
terminals and let us know the results. If I am the only one with these
problems, then I need to dig deeper.
Vern
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