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nuckolls.bob(at)aeroelect
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 Posted: Tue Jul 06, 2021 3:58 pm Post subject: Melted battery contractor ground wire |
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At 03:15 PM 7/6/2021, you wrote:
| Quote: | Hello Frank,
You are asking good questions.
What typically happens is the coil burns up and causes an open circuit, but in your case it appears to have failed closed.
It will be interesting to conduct a post-mortem on it to determine how it created such a hard fault. |
We've inspected a few failures here over the
years but a hard fault across the coil is
a new one.
Here's an exemplar 'open' coil
https://tinyurl.com/yzcx4q2u
If you have no other plans for the failed
part, I'd like to have it.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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nuckolls.bob(at)aeroelect
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| Posted: Tue Jul 06, 2021 4:02 pm Post subject: Melted battery contractor ground wire |
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At 01:20 PM 7/6/2021, you wrote:
| Quote: | --> AeroElectric-List message posted by: "frank3" <frank3phyl(at)comcast.net>
This experience makes me wonder why no circuit protection for the contactor activator switch circuit in any of the architectures.
Maybe it's because a short in the contactor is unlikely, as Joe says, but isn't that the assumption behind all circuits that do have circuit protection built in? |
The vast majority of failures in wires
is a lost of continuity. Broken wire,
loose terminal, etc. The battery contactor
control wire is generally never at-risk
for fault to ground on the run between
contactor and master switch . . . the master
contactor simply becomes 'stuck on'.
The fault you've experienced is exceedingly
rare . . . the first one I've heard of.
It would be interesting to identify and
document the failure mode.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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nuckolls.bob(at)aeroelect
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| Posted: Wed Jul 07, 2021 5:25 pm Post subject: Melted battery contractor ground wire |
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| Quote: |
Bob, if you still want the contactor I'll gladly send it to you. Just let me know where to send. |
Bob Nuckolls
PO Box 130
Medicine Lodge, Kansas 67104-0130
| Quote: | | Thanks everyone for you interest and advice. I have ordered a new contactor from our friends at B&C. |
Was this contactor from B&C originally? Which
part?
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Thu Jul 08, 2021 3:32 pm Post subject: Melted battery contractor ground wire |
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At 12:59 PM 7/8/2021, you wrote:
| Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>
I think that jluckey has solved the problem. Reverse battery polarity explains the melted wire and the blown fuse. Luckily the EFIS was not damaged.
I predict that Bob N will not find anything wrong with the contactor. An over voltage event is extremely unlikely without an alternator running.
It is pretty easy to reverse battery voltage when using jumper cables. One has a 50-50 chance of getting it wrong. |
agreed. in fact, the spike suppression diode
served to PROTECT against reversed polarity.
It would have prevented contactor closing by
shunting the applied voltage to near zero and
thus causing the wire to melt.
This suggests a reason for including a fuse
in the battery contactor control line . . .
it would prevent wire and fuse damage in
the reverse polarity event.
Perhaps a fusible link? 24AWG against a
20AWG control line? Perhaps a bit more
robust mechanically. But this should
be an exceedingly rare event.
If you've not yet mailed the contactor,
I suggest you re-install it and see what
happens.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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nuckolls.bob(at)aeroelect
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| Posted: Sun Aug 01, 2021 4:50 pm Post subject: Melted battery contractor ground wire |
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Frank,
As we suspected, your battery contactor is just fine.
Would you like for me to mail it back?
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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