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GrummanDude
Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA
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 Posted: Wed Jun 24, 2015 12:32 pm Post subject: Wiring: Burned |
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Over the last couple of years, more so recently, I’ve been replacing burned switches and some wiring to the Tail Nav and Flashing Beacon. The wire is burning. I had one incident of the wire to the master relay burning. The indication is the wire bubbles and, in some cases, burns completely through.
More and more people are leaving the Nav and Beacon lights on continuously. I don’t think they were intended to do this, but I wasn’t there so I’m just guessing.
Last Friday, a customer brought in a (late) 1976 Tiger for an annual. He asked me to look into a left fuel gauge always reading full. I started at the left sending unit and worked my way up. When I got to the gauge, I found a very burned Nav Light wire. The connector was burned. I started taking the wiring bundle apart and found a lot of burned wires. I mean, every wire in the bundle that plugs into the connector was burned; including the fuel gauge wires. I ended up replacing all of the wire for the Tail Nav and Beacon from the connector (I had to replace the connector it was so badly burned) to the tail with 18AWG wire. The Nav light wires to the wings were OK.
If you are on my AuCountry Aviation Facebook page, you can see all of the pics.
[img]cid:C415178A-22A0-4A9C-9FCA-739483B042FA[/img]
[img]cid:F348F0A7-DC63-4093-8867-7C0CFE37571B[/img]
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_________________
Gary
AuCountry Aviation
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flying-nut(at)cfl.rr.com
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| Posted: Wed Jun 24, 2015 12:54 pm Post subject: Wiring: Burned |
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Wed Jun 24, 2015 1:09 pm Post subject: Wiring: Burned |
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Linn, Â
nothing in the body of the email.
BarryÂ
On Wednesday, June 24, 2015, Linn Walters <flying-nut(at)cfl.rr.com (flying-nut(at)cfl.rr.com)> wrote:
--
Sent from Gmail Mobile
[quote][b]
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flying-nut(at)cfl.rr.com
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| Posted: Wed Jun 24, 2015 2:00 pm Post subject: Wiring: Burned |
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Nothing in my copy either, but if you view 'message source' .... it's there. I'll resend.
Linn
On 6/24/2015 5:08 PM, FLYaDIVE wrote:
[quote]Linn, Â
nothing in the body of the email.
BarryÂ
On Wednesday, June 24, 2015, Linn Walters <flying-nut(at)cfl.rr.com (flying-nut(at)cfl.rr.com)> wrote:
--
Sent from Gmail Mobile
No virus found in this message.
Checked by AVG - www.avg.com
Date: 06/24/15 [b]
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Wed Jun 24, 2015 2:05 pm Post subject: Wiring: Burned |
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HMmmmmm. Where is "message source"?
Barry
On Wednesday, June 24, 2015, Linn Walters <flying-nut(at)cfl.rr.com (flying-nut(at)cfl.rr.com)> wrote:
| Quote: | Nothing in my copy either, but if you view 'message source' .... it's there. I'll resend.
Linn
On 6/24/2015 5:08 PM, FLYaDIVE wrote:
| Quote: | Linn, Â
nothing in the body of the email.
BarryÂ
On Wednesday, June 24, 2015, Linn Walters <[url=javascript:_e(%7B%7D,'cvml','flying-nut(at)cfl.rr.com');]flying-nut(at)cfl.rr.com[/url]> wrote:
--
Sent from Gmail Mobile
No virus found in this message.
Checked by AVG - www.avg.com
Date: 06/24/15
st" target="_blank">http://www.matronics.com/Navigator?TeamGrumman-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
|
|
--
Sent from Gmail Mobile
[quote][b]
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flying-nut(at)cfl.rr.com
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| Posted: Wed Jun 24, 2015 2:14 pm Post subject: Wiring: Burned |
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Second try failed too.
I use Thunderbird as my email client. Under the 'view' button on the menu is 'message source' or you can use ctrl-u.
However, here's what I said .... without Gary's original, quoted, email.
Linn ...... am I repeating myself???
| Quote: | Gary, the problem isn't with the load being on .... the problem most
likely is that the breaker/fuse is too large (or broke) for the current
capability of the wire. Current high enough to do this much damage to
the wire should have tripped the breaker/fuse way before it got hot.
Breakers and fuses are there to protect the wire, not the devices attached.
I see a lot of problems where owners have 'robbed' power from existing
fuses and because they keep blowing just put in whatever fuse is
available in the junk box. When something happens way down the road,
such as a wire chafing through and going to ground, the wire becomes the
victim because the fuse could handle the current.
Linn
|
On 6/24/2015 6:05 PM, FLYaDIVE wrote:
[quote]HMmmmmm. Where is "message source"?
Barry
On Wednesday, June 24, 2015, Linn Walters <flying-nut(at)cfl.rr.com (flying-nut(at)cfl.rr.com)> wrote:
| Quote: | Nothing in my copy either, but if you view 'message source' .... it's there. I'll resend.
Linn
On 6/24/2015 5:08 PM, FLYaDIVE wrote:
|
--
Sent from Gmail Mobile
No virus found in this message.
Checked by AVG - www.avg.com
Date: 06/24/15 [b]
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Wed Jun 24, 2015 3:05 pm Post subject: Wiring: Burned |
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You are dead on Linn!
On Wednesday, June 24, 2015, Linn Walters <flying-nut(at)cfl.rr.com (flying-nut(at)cfl.rr.com)> wrote:
| Quote: | Second try failed too.
I use Thunderbird as my email client. Under the 'view' button on the menu is 'message source' or you can use ctrl-u.
However, here's what I said .... without Gary's original, quoted, email.
Linn ...... am I repeating myself???
| Quote: | Gary, the problem isn't with the load being on .... the problem most
likely is that the breaker/fuse is too large (or broke) for the current
capability of the wire. Current high enough to do this much damage to
the wire should have tripped the breaker/fuse way before it got hot.
Breakers and fuses are there to protect the wire, not the devices attached.
I see a lot of problems where owners have 'robbed' power from existing
fuses and because they keep blowing just put in whatever fuse is
available in the junk box. When something happens way down the road,
such as a wire chafing through and going to ground, the wire becomes the
victim because the fuse could handle the current.
Linn
|
On 6/24/2015 6:05 PM, FLYaDIVE wrote:
| Quote: | HMmmmmm. Where is "message source"?
Barry
On Wednesday, June 24, 2015, Linn Walters <[url=javascript:_e(%7B%7D,'cvml','flying-nut(at)cfl.rr.com');]flying-nut(at)cfl.rr.com[/url]> wrote:
| Quote: | Nothing in my copy either, but if you view 'message source' .... it's there. I'll resend.
Linn
On 6/24/2015 5:08 PM, FLYaDIVE wrote:
|
--
Sent from Gmail Mobile
No virus found in this message.
Checked by AVG - www.avg.com
Date: 06/24/15
st" target="_blank">http://www.matronics.com/Navigator?TeamGrumman-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
|
|
--
Sent from Gmail Mobile
[quote][b]
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teamgrumman(at)yahoo.com
Guest
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| Posted: Thu Jun 25, 2015 10:13 am Post subject: Wiring: Burned |
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I pulled the fuse and it was 10 amp. The wire that burned was 51LD3 (from the connector JP-1-1 to the junction with 5LD8/5LD11) and then 5LD4 to the tail light.
I agree, it should have blown the fuse. I have seen the Nav switch melted as well as the Pitot and the Flashing Beacon. I’m seeing more and more.
From now on, I have a line in my checklist to look at this connector.
The pics don’t come though the archive. Only the emails. If you are only signed up to the archive, you don’t get the pics.
They are, however, on the AuCountry Aviation Facebook page.
Gary
| Quote: | On Jun 24, 2015, at 4:05 PM, FLYaDIVE <flyadive(at)gmail.com (flyadive(at)gmail.com)> wrote:
You are dead on Linn!
On Wednesday, June 24, 2015, Linn Walters <flying-nut(at)cfl.rr.com (flying-nut(at)cfl.rr.com)> wrote: | Quote: | Second try failed too. I use Thunderbird as my email client. Under the 'view' button on the menu is 'message source' or you can use ctrl-u. However, here's what I said .... without Gary's original, quoted, email. Linn ...... am I repeating myself??? | Quote: | Gary, the problem isn't with the load being on ... the problem most
likely is that the breaker/fuse is too large (or broke) for the current
capability of the wire. Current high enough to do this much damage to
the wire should have tripped the breaker/fuse way before it got hot.
Breakers and fuses are there to protect the wire, not the devices attached.
I see a lot of problems where owners have 'robbed' power from existing
fuses and because they keep blowing just put in whatever fuse is
available in the junk box. When something happens way down the road,
such as a wire chafing through and going to ground, the wire becomes the
victim because the fuse could handle the current.
Linn
|
On 6/24/2015 6:05 PM, FLYaDIVE wrote:
| Quote: | HMmmmmm. Where is "message source"?
Barry On Wednesday, June 24, 2015, Linn Walters <[url=javascript:_e(%7B%7D,\'cvml\',\'flying-nut(at)cfl.rr.com\');]flying-nut(at)cfl.rr.com[/url]> wrote: | Quote: | Nothing in my copy either, but if you view 'message source' .... it's there. I'll resend. Linn On 6/24/2015 5:08 PM, FLYaDIVE wrote:
| Quote: | Linn,
nothing in the body of the email.
Barry On Wednesday, June 24, 2015, Linn Walters <flying-nut(at)cfl.rr.com> wrote:
-- Sent from Gmail Mobile
No virus found in this message. Checked by AVG - www.avg.com Date: 06/24/15 |
|
-- Sent from Gmail Mobile
No virus found in this message. Checked by AVG - www.avg.com Date: 06/24/15 |
|
-- Sent from Gmail Mobile | Quote: |
href="http://www.matronics.com/Navigator?TeamGrumman-List" class="">http://www.matronics.com/Navigator?TeamGrumman-List
class="">http://forums.matronics.com
class="">http://www.matronics.com/contribution
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[quote][b]
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Discover
Joined: 26 Feb 2007
Posts: 429
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| Posted: Sat Jul 04, 2015 6:33 am Post subject: Re: Wiring: Burned |
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Gary,
What gage is the 51LD3 wire?
I've looked at all your pictures to try and see the AWG indicated in the wire but can't make it out. Also, I spent an hour looking in the nainmrnance manual and parts manual and just can't find it.
Ned
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923te(at)att.net
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| Posted: Sat Jul 04, 2015 7:30 am Post subject: Wiring: Burned |
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Discover
Joined: 26 Feb 2007
Posts: 429
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| Posted: Sat Jul 04, 2015 8:28 am Post subject: Re: Wiring: Burned |
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Gary,
Just thinking out loud about your finding of several examples of Nav Light wires being toasted....
According to the Grumman Maintenance Manual it appears that the Navigation lights may be designed to be able to run continuously:
(See Attached photo below)
You can see from this chart that Navigation Lights are listed under things with "CONTINUOUS LOADS"
According to this chart the Nav lights, which basically is 3 light bulbs, pull 4.52 amps. Looking at the chart if you assume this fuse handles everything listed under Continuous except Battery Relay, Flashing Beacon and Pitot Heat you can figure the fuse sees 8.39 amps with the lights turned on. (26.49-18.1=8.39 amps)
Doesn't leave much room on the fuse.
Your wiring diagram schematic shows more than one wire connected to the 10 amp fuse in the buss bar:
http://www.aucountry.com/ACA_Folder/Technical/Wire_76-77.html
Fuel Gauge, Radio and Compass lights and 4 other Resistive loads denoted by an "R" that are not labeled that I'm guessing are lights in the panel.
Without knowing the AWG the factory used for the wire I can't really continue doing any load analysis but I don't think you can properly protect one wire when two wires are connected to one fuse.
AC 43.13-1B TABLE 11-3. DC wire and circuit protector chart.
Shows for a 20 gauge wire you need a 5 amp fuse
18 gauge needs a 10 amp
But our fuse is "protecting" more than one wire. We could have one 20 gauge wire pulling 0 amps and the other pulling 9.9 amps. That would burn up the wire and not blow the fuse....
I'm not sure the fuse was the culprit here. I'm thinking that while good design would require it to protect the wire it doesn't always do it in this case.
I would suspect there are several culprits all due to age. Corrosion in the switch and connections and bulb holders all will make the resistance higher and cause more Amps to be drawn. The switches are really cheap to replace with new. I've had experience with switches causing resistance. Especially the master switch but also accessory switches. You can actually get pulsing panel/instrument lights from a corroded master switch....
I've seen lots of bulb sockets that are corroded. And a few connectors where the actual metal spades inside the plastic are corroded. Ground wires get corroded where they are attached to the airframe. I've seen the fuse holders get corroded too. Adding more wires to a tightly packed bundle doesn't help either.
I'd be curious how all these things look on the planes you've found the burnt wires
Regards,
Ned
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teamgrumman(at)yahoo.com
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| Posted: Sat Jul 04, 2015 10:07 am Post subject: Wiring: Burned |
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My personal opinion is that whoever made up the wiring diagram knew they were limited by panel space to put fuses/circuit breakers. The wire from the switch to the branch that splits off for the wing and tail lights should be “at least” 18 AWG and I would have gone higher. Each of the wires after the split could be 20 AWG. I’d still use 18 AWG. The ground wire on the tail Nav and beacon is just a screw through the ELT tray. Not great.
The plastic wire cracks and corrosion within the wiring adds to the current draw. It’s just not a great design. It’s OK. Probably State-of-the-art in 1969.
| Quote: | On Jul 4, 2015, at 9:29 AM, Discover <923te(at)cox.net> wrote:
Gary,
Just thinking out loud about your finding of several examples of Nav Light wires being toasted....
According to the Grumman Maintenance Manual it appears that the Navigation lights may be designed to be able to run continuously:
image1.jpeg
You can see from this chart that Navigation Lights are listed under things with "CONTINUOUS LOADS"
According to this chart the Nav lights, which basically is 3 light bulbs, pull 4.52 amps. Looking at the chart if you assume this fuse handles everything listed under Continuous except Battery Relay, Flashing Beacon and Pitot Heat you can figure the fuse sees 8.39 amps with the lights turned on. (26.49-18.1=8.39 amps)
Doesn't leave much room on the fuse.
Your wiring diagram schematic shows more than one wire connected to the 10 amp fuse in the buss bar:
http://www.aucountry.com/ACA_Folder/Technical/Wire_76-77.html
Fuel Gauge, Radio and Compass lights and 4 other Resistive loads denoted by an "R" that are not labeled that I'm guessing are lights in the panel.
Without knowing the AWG the factory used for the wire I can't really continue doing any load analysis but I don't think you can properly protect one wire when two wires are connected to one fuse.
AC 43.13-1B TABLE 11-3. DC wire and circuit protector chart.
Shows for a 20 gauge wire you need a 5 amp fuse
18 gauge needs a 10 amp
But our fuse is "protecting" more than one wire. We could have one 20 gauge wire pulling 0 amps and the other pulling 9.9 amps. That would burn up the wire and not blow the fuse....
I'm not sure the fuse was the culprit here. I'm thinking that while good design would require it to protect the wire it doesn't always do it in this case.
I would suspect there are several culprits all due to age. Corrosion in the switch and connections and bulb holders all will make the resistance higher and cause more Amps to be drawn. The switches are really cheap to replace with new. I've had experience with switches causing resistance. Especially the master switch but also accessory switches. You can actually get pulsing panel/instrument lights from a corroded master switch....
I've seen lots of bulb sockets that are corroded. And a few connectors where the actual metal spades inside the plastic are corroded. Ground wires get corroded where they are attached to the airframe. I've seen the fuse holders get corroded too. Adding more wires to a tightly packed bundle doesn't help either.
I'd be curious how all these things look on the planes you've found the burnt wires
Regards,
Ned
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