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Bad fast-on connection?

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khorton01(at)rogers.com
Guest

Posted: Mon May 09, 2011 3:27 pm Post subject: Bad fast-on connection?

I fought a GNS430W TX issue a while ago that was eventually apparently resolved by reseating the fast-on connector where the power line connects to the fuse block.  The radio had worked fine for 2.5 years, then suddenly was transmitting carrier only.   I ran out of ideas, so I eventually pulled the power connector off the fuse block, squeezed the fast-on a bit with pliers, and wiggled it back on, and the radio worked fine for five weeks.  Today it was not transmitting again.  I removed, squeezed and reinstalled the same fast-on connector again, and the problem appears to be solved, again.



I'm baffled by why this fast-on seems to be giving me grief.   Both the fast-on connectors and the fuse block were purchased from B&C Specialties, so I believe they are good quality.



I'm not sure what I should do to hopefully permanently fix the issue.  I'd appreciate any comments on the following possible courses of action, plus I'd love any other suggestions:



1. cut off the problem fast-on, splice the wire with a butt splice and install a new fast-on (the wire is not long enough to do this unless I splice it).



2. use dielectric grease on the connection, such as the Dynatex product sold by Stein Avionics:



http://www.steinair.com/chemicals.htm

http://www.accumetricinc.com/dynatex/PDF/49634.pdf



3. replace the Buss fuse block (purchased from B&C Specialites) with a new one.



4. bypass the fuse block with a ring terminal connected to the fuse block's input, and an inline fuse.  This gets rid of the fast-on connector in this circuit, but replaces it with a ring terminal.



Thanks,



--

Kevin Horton

RV-8

Ottawa, Canada

http://www.kilohotel.com/rv8

mapratherid(at)gmail.com
Guest

Posted: Mon May 09, 2011 5:01 pm Post subject: Bad fast-on connection?

Hi Kevin,



I'm sure you'll get other smart replies, but here are my thoughts..



- Have you done something to verify that it's a deficiency in the fast-on-spade interconnect?  Short of an alloy problem, an overheat, or ongoing mechanical stress, I have a tough time believing that's the problem.  

- Could it be that when you pull the fast-on off the spade, you're resetting some other connection in the functional chain?  A bad crimp? Some other loose connection?

- Is there another hot connection available on the fuse block?

- Is that an always-hot connection (battery bus)?

- I assume the fuse block is in the cabin where it stays dry and at a reasonable temperature...

- If you cut the connector off, save it for Bob..  He'll probably want to look at it.  



Matt-



On May 9, 2011, at 5:19 PM, Kevin Horton <khorton01(at)rogers.com> wrote:



 	  Quote: 	
		   

 

 I fought a GNS430W TX issue a while ago that was eventually apparently resolved by reseating the fast-on connector where the power line connects to the fuse block.  The radio had worked fine for 2.5 years, then suddenly was transmitting carrier only.   I ran out of ideas, so I eventually pulled the power connector off the fuse block, squeezed the fast-on a bit with pliers, and wiggled it back on, and the radio worked fine for five weeks.  Today it was not transmitting again.  I removed, squeezed and reinstalled the same fast-on connector again, and the problem appears to be solved, again.

 

 I'm baffled by why this fast-on seems to be giving me grief.   Both the fast-on connectors and the fuse block were purchased from B&C Specialties, so I believe they are good quality.

 

 I'm not sure what I should do to hopefully permanently fix the issue.  I'd appreciate any comments on the following possible courses of action, plus I'd love any other suggestions:

 

 1. cut off the problem fast-on, splice the wire with a butt splice and install a new fast-on (the wire is not long enough to do this unless I splice it).

 

 2. use dielectric grease on the connection, such as the Dynatex product sold by Stein Avionics:

 

 http://www.steinair.com/chemicals.htm

 http://www.accumetricinc.com/dynatex/PDF/49634.pdf

 

 3. replace the Buss fuse block (purchased from B&C Specialites) with a new one.

 

 4. bypass the fuse block with a ring terminal connected to the fuse block's input, and an inline fuse.  This gets rid of the fast-on connector in this circuit, but replaces it with a ring terminal.

 

 Thanks,

 

 --

 Kevin Horton

 RV-8

 Ottawa, Canada

 http://www.kilohotel.com/rv8

halbenjamin(at)optonline.
Guest

Posted: Mon May 09, 2011 6:46 pm Post subject: Bad fast-on connection?

Hi Kevin,

  

 My 2 cents is on the crimped connection of the fast on tab.  I don't know what size the wire is, but I'm guessing that it is very light gauge.  With the very light gauge wires (< 20AWG) I have better luck getting a good crimp by stripping twice the length of wire needed & folding in half prior to installing the terminal.  Hope this helps.

  

 Hal Benjamin

 RV-4, Long Island, NY

 On the last 999 items

  

 

---

nuckolls.bob(at)aeroelect
Guest

Posted: Mon May 09, 2011 6:59 pm Post subject: Bad fast-on connection?

At 08:09 PM 5/9/2011, you wrote:

 	  Quote: 	
		  



Hi Kevin,



I'm sure you'll get other smart replies, but here are my thoughts..



- Have you done something to verify that it's a deficiency in the 

fast-on-spade interconnect?  Short of an alloy problem, an overheat, 

or ongoing mechanical stress, I have a tough time believing that's 

the problem.

- Could it be that when you pull the fast-on off the spade, you're 

resetting some other connection in the functional chain?  A bad 

crimp? Some other loose connection?

- Is there another hot connection available on the fuse block?

- Is that an always-hot connection (battery bus)?

- I assume the fuse block is in the cabin where it stays dry and at 

a reasonable temperature...

- If you cut the connector off, save it for Bob..  He'll probably 

want to look at it.  


	


    Good suggestions Matt. I wish I knew where B&C buys

    inventory these days. There IS a potential problem

    with fast-ons crafted from softer alloys. The fact that

    you EVER had to 'tighten' this terminal gives one pause

    to wonder. Get a minimum 10-pak of these



http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=A0903-ND



    and use to replace the fast-on already installed.



    Also, see if you can exchange the 'problem' wire

    with another terminal that powers a lower current

    draw/less critical accessory.



    If you need to make a wire longer, use a soldered

    lap-splice under heatshrink to extend the wire.



http://www.aeroelectric.com/articles/Solder_Lap_Splicing/Solder_Lap_Splices.html





   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Mon May 09, 2011 7:01 pm Post subject: Bad fast-on connection?

At 08:09 PM 5/9/2011, you wrote:

 	  Quote: 	
		  



Hi Kevin,



I'm sure you'll get other smart replies, but here are my thoughts..



- Have you done something to verify that it's a deficiency in the 

fast-on-spade interconnect?  Short of an alloy problem, an overheat, 

or ongoing mechanical stress, I have a tough time believing that's 

the problem.

- Could it be that when you pull the fast-on off the spade, you're 

resetting some other connection in the functional chain?  A bad 

crimp? Some other loose connection?

- Is there another hot connection available on the fuse block?

- Is that an always-hot connection (battery bus)?

- I assume the fuse block is in the cabin where it stays dry and at 

a reasonable temperature...

- If you cut the connector off, save it for Bob..  He'll probably 

want to look at it.  


	


    Good suggestions Matt. I wish I knew where B&C buys

    inventory these days. There IS a potential problem

    with fast-ons crafted from softer alloys. The fact that

    you EVER had to 'tighten' this terminal gives one pause

    to wonder. Get a minimum 10-pak of these



http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=A0903-ND



    and use to replace the fast-on already installed.



    Also, see if you can exchange the 'problem' wire

    with another terminal that powers a lower current

    draw/less critical accessory.



    If you need to make a wire longer, use a soldered

    lap-splice under heatshrink to extend the wire.



http://www.aeroelectric.com/articles/Solder_Lap_Splicing/Solder_Lap_Splices.html





   Bob . . .

khorton01(at)rogers.com
Guest

Posted: Tue May 10, 2011 1:34 am Post subject: Bad fast-on connection?

On 2011-05-09, at 20:26 , Robert L. Nuckolls, III wrote:

 	  Quote: 	

 At 08:09 PM 5/9/2011, you wrote:

> 

> 

> Hi Kevin,

> 

> I'm sure you'll get other smart replies, but here are my thoughts..

> 

> - Have you done something to verify that it's a deficiency in the fast-on-spade interconnect?  Short of an alloy problem, an overheat, or ongoing mechanical stress, I have a tough time believing that's the problem.

> - Could it be that when you pull the fast-on off the spade, you're resetting some other connection in the functional chain?  A bad crimp? Some other loose connection?

> - Is there another hot connection available on the fuse block?

> - Is that an always-hot connection (battery bus)?

> - I assume the fuse block is in the cabin where it stays dry and at a reasonable temperature...

> - If you cut the connector off, save it for Bob..  He'll probably want to look at it.  

   Good suggestions Matt. I wish I knew where B&C buys

   inventory these days. There IS a potential problem

   with fast-ons crafted from softer alloys. The fact that

   you EVER had to 'tighten' this terminal gives one pause

   to wonder. Get a minimum 10-pak of these

 http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=A0903-ND

   and use to replace the fast-on already installed.

   Also, see if you can exchange the 'problem' wire

   with another terminal that powers a lower current

   draw/less critical accessory.

   If you need to make a wire longer, use a soldered

   lap-splice under heatshrink to extend the wire.

 http://www.aeroelectric.com/articles/Solder_Lap_Splicing/Solder_Lap_Splices.html

I am also having a very hard time believing that this connection is really the source of my problem.  But, everything else checked out good, and reseating this connector fixed the problem twice.

The power wire disappears into a wire bundle a few inches after the fast-on, so not much else could be disturbed when I reset the connector.  The wire itself is moved, the fast-on crimp might be disturbed, and something inside the fuse block might be disturbed.  That's about it I think.  Maybe the crimp is the real problem.

The fuse block is behind the instrument panel, accessible through a door on the back side of the forward luggage compartment, and is not open to the elements in any way.  It is not an always-hot bus.  It is the endurance bus in a classical Z-12 system architecture.

I'll order some new fast-ons from Digikey and throw out the stock I bought from B&C years ago.  Then I'll splice the wire and use a new fast-on.

Thanks for the advice.

--

Kevin Horton

RV-8

Ottawa, Canada

http://www.kilohotel.com/rv8

khorton01(at)rogers.com
Guest

Posted: Tue May 10, 2011 1:36 am Post subject: Bad fast-on connection?

Hal,



It's a 10a fuse, and I'm pretty sure the wire is 18 AWG. 



Kevin



On 2011-05-09, at 22:43 , halbenjamin(at)optonline.net wrote:



[quote] 

 Hi Kevin,

 

 My 2 cents is on the crimped connection of the fast on tab.  I don't know what size the wire is, but I'm guessing that it is very light gauge.  With the very light gauge wires (< 20AWG) I have better luck getting a good crimp by stripping twice the length of wire needed & folding in half prior to installing the terminal.  Hope this helps.

 

 Hal Benjamin

 RV-4, Long Island, NY

 On the last 999 items

 

 

 ---

nuckolls.bob(at)aeroelect
Guest

Posted: Tue May 10, 2011 5:55 am Post subject: Bad fast-on connection?

 	  Quote: 	
		  

I am also having a very hard time believing that this connection is 

really the source of my problem.  But, everything else checked out 

good, and reseating this connector fixed the problem twice.


	


     Yes . . . correlation does not necessarily translate

     to causation . . . but the evidence uncovered thus far

     is compelling.

 	  Quote: 	
		  The power wire disappears into a wire bundle a few inches after the 

fast-on, so not much else could be disturbed when I reset the 

connector.  The wire itself is moved, the fast-on crimp might be 

disturbed, and something inside the fuse block might be 

disturbed.  That's about it I think.  Maybe the crimp is the real problem.



The fuse block is behind the instrument panel, accessible through a 

door on the back side of the forward luggage compartment, and is not 

open to the elements in any way.  It is not an always-hot bus.  It 

is the endurance bus in a classical Z-12 system architecture.



I'll order some new fast-ons from Digikey and throw out the stock I 

bought from B&C years ago.


	


     Send them to me please . . .



 	  Quote: 	
		     Then I'll splice the wire and use a new fast-on.



Thanks for the advice.


	


     We've had the butt-uglies rear their heads on

     several fast-on installations over the years with

     a very few instances where there was no clear causation

     other than to chalk it up to loss of gas-tightness

     somewhere.



     I presume there's no evidence of discoloration that

     can be attributed to overheating. This leaves us

     with simple corrosion as a byproduct of loss of

     force in the joint. Perhaps you'll discover new

     information as you proceed.



     Keep us apprised of your efforts and findings.

   Bob . . .

fvalarm(at)rapidnet.net
Guest

Posted: Tue May 10, 2011 8:07 am Post subject: Bad fast-on connection?

Would a conductive paste applied to the spade before attaching the faston

help to keep the joint free of all things that facilitate corrosion?  Would

such a paste handle the heat of the joint?



Bevan 



--

nuckolls.bob(at)aeroelect
Guest

Posted: Tue May 10, 2011 3:42 pm Post subject: Bad fast-on connection?

At 12:03 PM 5/10/2011, you wrote:

 	  Quote: 	
		  



Would a conductive paste applied to the spade before attaching the faston

help to keep the joint free of all things that facilitate corrosion?  Would

such a paste handle the heat of the joint?


	


   It doesn't need to be conductive. See articles on the

   characteristics of gas-tight terminations. Nor does

   the "additive" need to be high temperature. The ideal

   joint by definition has very low resistance . . . i.e.

   very low loss, very low temperature rise.



   If the joints in question were flat-surface to flat-surface,

   some sort of moisture exclusion is sometimes helpful.

   Any sort of durable grease fills the voids in the joint

   and excludes moisture. In the case of fast-ons, the

   'magic' happens at a very high pressure connection

   between the tab and the terminal.  See



http://www.aeroelectric.com/articles/faston3.pdf



   Failures in these joints tend to be related to

   loss of force that compromises make-up pressure.

   Some moisture excluding grease wouldn't hurt

   anything . . . but I'm not visualizing how it

   would help. Loss of make up force is critical.

   Bob . . .

eschlanser

Joined: 08 Apr 2010
Posts: 60

Posted: Tue May 10, 2011 5:09 pm Post subject: Re: Bad fast-on connection?

I know fast-on connectors are preferred here but I have heard that Cessna tested and rejected the use of them due to some kind of problems. They might have been problems such as you are having. Perhaps, someone here can shed light on the reasons for Cessna's rejection. I didn't find it in the AeroElectric Connection Book.  My avionics advisor is questioning me using them because that isn't the way it is done at his shop.

Eric

nuckolls.bob(at)aeroelect
Guest

Posted: Tue May 10, 2011 6:09 pm Post subject: Bad fast-on connection?

At 09:09 PM 5/10/2011, you wrote:

 	  Quote: 	
		  



I know fast-on connectors are preferred here but I have heard that 

Cessna tested and rejected the use of them due to some kind of 

problems. They might have been problems such as you are having. 

Perhaps, someone here can shed light on the reasons for Cessna's 

rejection. I didn't find it in the AeroElectric Connection Book.  My 

avionics advisor is questioning me using them because that isn't the 

way it is done at his shop.


	


    I wouldn't say they are "preferred" . . . if one has

    the budget and/or the desire to do anything else with

    legacy hardware, the risks are low.



    Actually, Cessna put them in first. It was during the

    transition from round-hole toggle and push-pull switches

    to the rectangular-hole rocker switches that the entire

    single-engine line went to .250" fast-ons on the rear

    of the switches.



http://www.aeroelectric.com/articles/Progressive-Xfr_Split-Rocker_Switches.pdf



    There have been plenty field-failures associated with

    this switch/terminal combination. I've investigated some.

    Most involved loss of connection integrity in the riveted

    joints for the switches and/or the low pressure connection

    at the switch's center pivot. Only a few were attributable

    to loss of fast-on-to-tab connectivity.



http://aeroelectric.com/Pictures/Switches/Carling_Cutaway.jpg



http://aeroelectric.com/Pictures/Switches/Carling_Failures/



    So in fact, there were tens of thousands of Cessna S.E.

    aircraft per year produced for a goodly number of years

    that featured this technology.



    Equal or better than Honeywell-Microswitch and ring

    terminals . . . or better yet, soldered posts? Depends

    on what you call "better".



    Failure rates will be higher with the less robust product

    (and for different reasons) but we're designing and building

    failure tolerant airplanes. Further, we expect failure rates

    to be no worse than that experienced by the single engine fleet

    at Cessna.



    I'm aware of no ADs to swap out all the rockers in the

    venerable ol' Pawnee Plant airplanes. But there IS an

    AD against the equally venerable W31 switch/breaker in

    Bonanzas and Barons that generates a bit of smoke from

    time to time on a lot fewer airplanes.



    So hanging my hat on demonstrable experience gleaned over

    decades of field history suggests that the fast-on terminal

    system is of good value and presents no extra-ordinary risks.

    But if you prefer something else . . . no problem.

   Bob . . .

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