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Melted wire
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teamgrumman(at)yahoo.com
Guest

Posted: Thu Sep 20, 2012 6:28 pm Post subject: Melted wire

One of the Tigers I maintain started having that old wire burning smell.  Not all the time.  Off and on.  Smoke once.  Never repeatable.  

A mechanic outside Oshkosh identified 51PA3 as having a 'rough, bubbly surface.'  This wire was under the panel toward the middle in a bundle of wires.  

Yesterday, I found the same thing without the knowledge of the previous find.  51PA3 is a ground wire.  No circuit breaker or fuse.  

I followed the wire to the engine side and noticed several melted looking areas.

Figuring the wire needed to be replaced anyway, I cut into it and put an ammeter in series.  The battery relay that is energized by adding ground the the middle terminal is at the end of the wire.

This wire drew 0.065 to 0.70 amps.  The really odd thing was that it got really hot while I was holding it.  

I replaced it with No.18 wire.  The removed wire had a LOT of places on the wire  where the shielding had either been melted or worn away; I couldn't tell why the shielding was missing.  The wire in those areas was very corroded.  

Anyone else ever seen anything like that?

        From: Bob Steward <n76lima(at)mindspring.com>

 To: teamgrumman-list(at)matronics.com 

 Sent: Thursday, September 20, 2012 5:49 PM

 Subject: Re: Brake Reservoir Relocated?

  

 

 --> TeamGrumman-List message posted by: Bob Steward <n76lima(at)mindspring.com (n76lima(at)mindspring.com)>



I worked on a Traveler that had been modified like that.

Worked fine, but could have been better engineered.

--Bob St=          - The TeamGrumman-List Email Forum -<= Same great content also                      &nbs===================



 

 

  

 [quote][b]

teamgrumman(at)yahoo.com
Guest

Posted: Sat Sep 22, 2012 8:13 pm Post subject: Melted wire

No ones ever heard of this?

Gary

Sent from my iPad



On Sep 20, 2012, at 7:27 PM, Gary Vogt <teamgrumman(at)yahoo.com (teamgrumman(at)yahoo.com)> wrote:



[quote]One of the Tigers I maintain started having that old wire burning smell.  Not all the time.  Off and on.  Smoke once.  Never repeatable.  

A mechanic outside Oshkosh identified 51PA3 as having a 'rough, bubbly surface.'  This wire was under the panel toward the middle in a bundle of wires.  

Yesterday, I found the same thing without the knowledge of the previous find.  51PA3 is a ground wire.  No circuit breaker or fuse.  

I followed the wire to the engine side and noticed several melted looking areas.

Figuring the wire needed to be replaced anyway, I cut into it and put an ammeter in series.  The battery relay that is energized by adding ground the the middle terminal is at the end of the wire.

This wire drew 0.065 to 0.70 amps.  The really odd thing was that it got really hot while I was holding it.  

I replaced it with No.18 wire.  The removed wire had a LOT of places on the wire  where the shielding had either been melted or worn away; I couldn't tell why the shielding was missing.  The wire in those areas was very corroded.  

Anyone else ever seen anything like that?

        From: Bob Steward <n76lima(at)mindspring.com (n76lima(at)mindspring.com)>

 To: teamgrumman-list(at)matronics.com (teamgrumman-list(at)matronics.com) 

 Sent: Thursday, September 20, 2012 5:49 PM

 Subject: Re: Brake Reservoir Relocated?

  

 

 --> TeamGrumman-List message posted by: Bob Steward <n76lima(at)mindspring.com (n76lima(at)mindspring.com)>



I worked on a Traveler that had been modified like that.

Worked fine, but could have been better engineered.

--Bob St=          - The TeamGrumman-List Email Forum -<= Same great content also                      &nbs===================



 

 

  

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[b]

n76lima(at)mindspring.com
Guest

Posted: Sat Sep 22, 2012 8:35 pm Post subject: Melted wire

You're saying that this is a shielded GROUND wire?

Haven't had a chance to look at the manual schematics to see what circuit 51PA3 is part of.

Can't imagine the need for a shielded ground (except the P-leads).

--Bob Steward

radiohound(at)AOL.COM
Guest

Posted: Sat Sep 22, 2012 8:42 pm Post subject: Melted wire

Go to sleep, bob, day of rest and all.



Restful Woofs from the boys



Frank

850-819-1666



On Sep 22, 2012, at 11:35 PM, Bob Steward <n76lima(at)mindspring.com> wrote:



 	  Quote: 	
		   

 

 You're saying that this is a shielded GROUND wire?

 Haven't had a chance to look at the manual schematics to see what circuit 51PA3 is part of.

 Can't imagine the need for a shielded ground (except the P-leads).

 --Bob Steward

n76lima(at)mindspring.com
Guest

Posted: Sat Sep 22, 2012 8:49 pm Post subject: Melted wire

I found 51PA4 wire code for the ground from the battery side of the Master Switch to the airframe ground on the 70's Tigers and Cheetahs. This is a ~6" long segment of plain, unshielded wire with a 1/4" female spade terminal at the Master and a #6 ring terminal on the other end that grounds to the honeycomb with a #4 sheet metal screw.

The normal convention is that each segment in a circuit has the next # as the last digit.

So there SHOULD be 3 previous segments in this circuit.  There are not.

What does your 51PA3 connect to?

--Bob Steward

n76lima(at)mindspring.com
Guest

Posted: Sat Sep 22, 2012 8:50 pm Post subject: Melted wire

Gary has me stirred up over this.

N200FW canopy plastic looks very nice, if I do say so myself!

--Bob

Frank Sundram <radiohound(at)AOL.COM> wrote:

 	  Quote: 	

Go to sleep, bob, day of rest and all.

Restful Woofs from the boys

Frank

850-819-1666

On Sep 22, 2012, at 11:35 PM, Bob Steward <n76lima(at)mindspring.com> wrote:

> 

> 

> You're saying that this is a shielded GROUND wire?

> Haven't had a chance to look at the manual schematics to see what circuit 51PA3 is part of.

> Can't imagine the need for a shielded ground (except the P-leads).

> --Bob Steward

> 

> 

> 

> 

>

beltz6

Joined: 31 May 2008
Posts: 10
Location: Goleta, CA

Posted: Sun Sep 23, 2012 7:37 am Post subject: Re: Melted wire

 	  n76lima(at)mindspring.com wrote: 	
		  I found 51PA4 wire code for the ground from the battery side of the Master Switch to the airframe ground on the 70's Tigers and Cheetahs. This is a ~6" long segment of plain, unshielded wire with a 1/4" female spade terminal at the Master and a #6 ring terminal on the other end that grounds to the honeycomb with a #4 sheet metal screw.

The normal convention is that each segment in a circuit has the next # as the last digit.

So there SHOULD be 3 previous segments in this circuit.  There are not.

What does your 51PA3 connect to?

--Bob Steward 	




I think MAYBE Gary meant 5PA3, not 51PA3 (??).  It's the one that connects the battery solenoid to the battery side of the master switch.



Yeah, it's my plane that smoked up and started this thread :-/

beltz6

Joined: 31 May 2008
Posts: 10
Location: Goleta, CA

Posted: Sun Sep 23, 2012 7:50 am Post subject: Re: Melted wire

Here are some pics of various segments of the wire in question that was removed:



http://i.imgur.com/kBcmw.jpg

http://i.imgur.com/lSQGa.jpg

http://i.imgur.com/cNPxn.jpg

http://i.imgur.com/SuYSu.jpg



You can clearly see a "51PA3" stamped on in one image, but this wire shows up as "5PA3" in the diagrams I'm looking at.

teamgrumman(at)yahoo.com
Guest

Posted: Sun Sep 23, 2012 10:29 am Post subject: Melted wire

no, the plastic shield, insulation, whatever, was melted.  it goes from the battery relay to the master.  it's the ground wire.  it got VERY hot drawing .7 amps.

        From: Bob Steward <n76lima(at)mindspring.com>

 To: teamgrumman-list(at)matronics.com 

 Sent:  Saturday, September 22, 2012 9:35 PM

 Subject: Re: Melted wire

 --> TeamGrumman-List message posted by: Bob Steward <n76lima(at)mindspring.com (n76lima(at)mindspring.com)>

You're saying that this is a shielded GROUND wire?

Haven't had a chance to look at the manual schematics to see what circuit 51PA3 is part of.

Can't imagine the need for a shield========================

grumpyparts

Joined: 28 Jan 2009
Posts: 65
Location: EGHH

Posted: Sun Sep 23, 2012 10:30 am Post subject: Re: Melted wire

The 51 indicated it was used on the AA1 as well as AA5. I assume this cable was taken from a late model AA5 after the AA1 line was closed.

teamgrumman(at)yahoo.com
Guest

Posted: Sun Sep 23, 2012 10:31 am Post subject: Melted wire

look on my wiring diagram.  it's marked 5PA3 since it is one of the original 5 series wires.  in the plane it's marked 51PA3

        From: Bob Steward <n76lima(at)mindspring.com>

 To: teamgrumman-list(at)matronics.com 

 Sent: Saturday, September 22, 2012 9:50 PM

 Subject: Re: Melted wire

 --> TeamGrumman-List message posted by: Bob Steward <n76lima(at)mindspring.com (n76lima(at)mindspring.com)>

Gary has me stirred up over this.

N200FW canopy plastic looks very nice, if I do say so myself!

--Bob

Frank Sundram <radiohound(at)AOL.COM (radiohound(at)AOL.COM)> wrote:

 	  Quote: 	
		  --> TeamGrumman-List message posted by: Frank Sundram <radiohound(at)aol.com (radiohound(at)aol.com)>

Go to sleep, bob, day of rest and all.

Restful Woofs from the boys

Frank

850-819-1666

On Sep 22, 2012, at 11:35 PM, Bob Steward <n76lima(at)mindspring.com (n76lima(at)mindspring.com)> wrote:

> --> TeamGrumman-List message posted by:  Bob Steward <n76lima(at)mindspring.com (n76lima(at)mindspring.com)>

> 

> You're saying that this is a shielded GROUND wire?

> Haven't had a chance to look at the manual schematics to see what circuit 51PA3 is part of.

> Can't imagine the need for a shielded ground (except the P-leads).

> --Bob Steward

> 

> 

> 

> 

> 

;  --> sp;                     -================

 [quote][b]

n76lima(at)mindspring.com
Guest

Posted: Sun Sep 23, 2012 11:36 am Post subject: Melted wire

This STILL makes no sense.  The Master Relay resistance is ~15 ohms.  So the current should be in the 0.8 amps, and the energy dissipated is ~9.6 watts.

Certainly not enough to heat the wire.

So SOMETHING is causing a dead short from Master Solenoid to ground.  I'd be checking the Master Solenoid for some sort of internal short.

That is unless someone has improperly replaced the Continuous Duty Master Solenoid with an Intermittent Duty Starter Solenoid...

That would mean a ~6 amp draw, dissipating 72 watts!

Your ammeter reading would suggest otherwise.

--Bob Steward

Birmingham, AL

beltz6

Joined: 31 May 2008
Posts: 10
Location: Goleta, CA

Posted: Sun Sep 23, 2012 11:53 am Post subject: Re: Melted wire

 	  n76lima(at)mindspring.com wrote: 	
		  This STILL makes no sense.  The Master Relay resistance is ~15 ohms.  So the current should be in the 0.8 amps, and the energy dissipated is ~9.6 watts.

Certainly not enough to heat the wire.

So SOMETHING is causing a dead short from Master Solenoid to ground.  I'd be checking the Master Solenoid for some sort of internal short.

That is unless someone has improperly replaced the Continuous Duty Master Solenoid with an Intermittent Duty Starter Solenoid...

That would mean a ~6 amp draw, dissipating 72 watts!

Your ammeter reading would suggest otherwise.

--Bob Steward

Birmingham, AL 	




Someone where I work has a wrap-around ammeter.  I'm going to check that wire again to make sure it's carrying in the .7-.8 amp ballpark.



Also, how hard would it be to get to the right terminals on the master solenoid to check its internal resistance?

teamgrumman(at)yahoo.com
Guest

Posted: Sun Sep 23, 2012 5:15 pm Post subject: Melted wire

IF there is a significant corrosion in the areas where the plastic shield is, would there be enough resistance to make the wire heat more?

I replaced the entire wire with #18 wire.

        From: Bob Steward  <n76lima(at)mindspring.com>

 To: teamgrumman-list(at)matronics.com 

 Sent: Sunday, September 23, 2012 12:35 PM

 Subject: Re: Melted wire

 --> TeamGrumman-List message posted by: Bob Steward <n76lima(at)mindspring.com (n76lima(at)mindspring.com)>

This STILL makes no sense.  The Master Relay resistance is ~15 ohms.  So the current should be in the 0.8 amps, and the energy dissipated is ~9.6 watts.

Certainly not enough to heat the wire.

So SOMETHING is causing a dead short from Master Solenoid to ground.  I'd be checking the Master Solenoid for some sort of internal short.

That is unless someone has improperly replaced the Continuous Duty Master Solenoid with an Intermittent Duty Starter Solenoid...

That would mean a ~6 amp draw, dissipating 72 watts!

Your ammeter reading would suggest otherwise.

--Bob Steward<= Use the =             - List Contribution Web Site                      &nbs

 [quote][b]

n76lima(at)mindspring.com
Guest

Posted: Sun Sep 23, 2012 6:45 pm Post subject: Melted wire

[Gary] IF there is a significant corrosion in the areas where the plastic shield is, would there be enough resistance to make the wire heat more?  I replaced the entire wire with #18 wire.



The problem is that the power is applied to the coil internally in the Master Relay, and then this wire is a GROUND.  A #2 gauge jumper cable would not carry anymore current than the OEM wire, because the limiting resistance is at the SOURCE (power goes through the positive cable to the Master Relay, and then to the coil internally, and finally to a ground via the wire in question).  One can't really lower the resistance of the circuit by fiddling with the ground wire.  One can INCREASE the resistance, and thereby lessen the current, but no way to externally to the Master Relay LOWER the resistance.  So "corrosion" on the wire would have no effect at increasing the current enough to heat it.  I suppose if enough strands were corroded through that the current of ~0.8 amps would heat the wire locally, but the insulation would have to be off and the corrosion damage happen BEFORE the heating, and since the supposition is that the wire got hot FIRST, damaging the insulation, which could then lead to the corrosion and the narrowing of the wire, the chain is completely backwards.  And after the FIRST area was damaged (by whatever means), then no further damage could occur down stream, since the current would now be even MORE limited by the increased resistance at the first site damaged on the wire.



With several areas of damage, and wide spread lengths of heating, this is NOT a localized problem of the wire losing a few strands to corrosion.



Hence my suggestion that someone had replaced the Master Relay with a Starter Relay, or that the relay had some sort of internal fault that was shorting power to ground that did not go through the 15 ohm coil.



--Bob Steward

flyv35b(at)minetfiber.com
Guest

Posted: Mon Sep 24, 2012 5:36 am Post subject: Melted wire

On 9/23/2012 7:45 PM, n76lima(at)mindspring.com wrote:

 	  Quote: 	
		   



 [Gary] IF there is a significant corrosion in the areas where the plastic shield is, would there be enough resistance to make the wire heat more?  I replaced the entire wire with #18 wire.



 The problem is that the power is applied to the coil internally in the Master Relay, and then this wire is a GROUND.  A #2 gauge jumper cable would not carry anymore current than the OEM wire, because the limiting resistance is at the SOURCE (power goes through the positive cable to the Master Relay, and then to the coil internally, and finally to a ground via the wire in question).  One can't really lower the resistance of the circuit by fiddling with the ground wire.  One can INCREASE the resistance, and thereby lessen the current, but no way to externally to the Master Relay LOWER the resistance.  So "corrosion" on the wire would have no effect at increasing the current enough to heat it.  I suppose if enough strands were corroded through that the current of ~0.8 amps would heat the wire locally, but the insulation would have to be off and the corrosion damage happen BEFORE the heating, and since the supposition is that the wire got hot FIRST, damaging the insulation, wh

 
	


 i!

 	  Quote: 	
		  

   ch could then lead to the corrosion and the narrowing of the wire, the chain is completely backwards.  And after the FIRST area was damaged (by whatever means), then no further damage could occur down stream, since the current would now be even MORE limited by the increased resistance at the first site damaged on the wire.



 With several areas of damage, and wide spread lengths of heating, this is NOT a localized problem of the wire losing a few strands to corrosion.



 Hence my suggestion that someone had replaced the Master Relay with a Starter Relay, or that the relay had some sort of internal fault that was shorting power to ground that did not go through the 15 ohm coil.



 --Bob Steward



Bob, what's the current draw of the coil in a starter contactor?  Would 
	


that even be enough to melt the insulation of an 18 ga wire?  I assume 

the wire was 18 ga.  A single 18ga wire in free air wire should be able 

to handle nearly 25 amp at conductor temp of around 150 C (100 C above 

ambient).  How would you get that kind of current flow without a direct 

short to ground?



Cliff

n76lima(at)mindspring.com
Guest

Posted: Mon Sep 24, 2012 6:52 am Post subject: Melted wire

The coil in the Starter should have a resistance of ~2 ohms.  So that means a current of ~6 amps (at) 12V.

Far below what the 18 ga. wire should safely carry.

The starter relay is usually wired differently than the Master. The Starter usually has the coil isolated from the power terminals, and is POWERED by the start button switch, rather than grounded.

It is also protected by the 10 amp fuse that powers the start/fuel pump/strobe circuit.

So the wire powering the Starter relay is not subject to a ground fault, since it would pop the 10 amp fuse before heating the wire.

The Master wiring might be subject a ground fault if some internal fault in the relay allowed a lower resistance in the relay to overload the ground wire.

--Bob Steward

tigerized(at)gmail.com
Guest

Posted: Mon Sep 24, 2012 7:08 am Post subject: Melted wire

I'm guessing here, without a wiring diagram in front of me, but wouldn't a poor mechanical ground to the body of the starter solenoid result in all current going through the 18 ga. wire instead?



If so, that would overheat the wire for sure.

 

Rick



On Mon, Sep 24, 2012 at 7:50 AM, Bob Steward <n76lima(at)mindspring.com (n76lima(at)mindspring.com)> wrote:

[quote] --> TeamGrumman-List message posted by: Bob Steward <n76lima(at)mindspring.com (n76lima(at)mindspring.com)>

 

 The coil in the Starter should have a resistance of ~2 ohms.  So that means a current of ~6 amps (at) 12V.

 Far below what the 18 ga. wire should safely carry.

 The starter relay is usually wired differently than the Master. The Starter usually has the coil isolated from the power terminals, and is POWERED by the start button switch, rather than grounded.

 It is also protected by the 10 amp fuse that powers the start/fuel pump/strobe circuit.

 So the wire powering the Starter relay is not subject to a ground fault, since it would pop the 10 amp fuse before heating the wire.

 The Master wiring might be subject a ground fault if some internal fault in the relay allowed a lower resistance in the relay to overload the ground wire.

 --Bob Steward

 

 

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JHOSLER(at)epri.com
Guest

Posted: Mon Sep 24, 2012 7:11 am Post subject: Melted wire

The OEM ran the ground wire to the airframe with a sheet metal screw????

 

John

 

From: owner-teamgrumman-list-server(at)matronics.com [mailto:owner-teamgrumman-list-server(at)matronics.com] On Behalf Of Rick Lindstrom

Sent: Monday, September 24, 2012 11:08 AM

To: teamgrumman-list(at)matronics.com

Subject: Re: Re: Melted wire



 

I'm guessing here, without a wiring diagram in front of me, but wouldn't a poor mechanical ground to the body of the starter solenoid result in all current going through the 18 ga. wire instead?



If so, that would overheat the wire for sure.



Rick

On Mon, Sep 24, 2012 at 7:50 AM, Bob Steward <n76lima(at)mindspring.com (n76lima(at)mindspring.com)> wrote:

--> TeamGrumman-List message posted by: Bob Steward <n76lima(at)mindspring.com (n76lima(at)mindspring.com)>



The coil in the Starter should have a resistance of ~2 ohms.  So that means a current of ~6 amps (at) 12V.

Far below what the 18 ga. wire should safely carry.

The starter relay is usually wired differently than the Master. The Starter usually has the coil isolated from the power terminals, and is POWERED by the start button switch, rather than grounded.

It is also protected by the 10 amp fuse that powers the start/fuel pump/strobe circuit.

So the wire powering the Starter relay is not subject to a ground fault, since it would pop the 10 amp fuse before heating the wire.

The Master wiring might be subject a ground fault if some internal fault in the relay allowed a lower resistance in the relay to overload the ground wire.

--Bob Steward

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n76lima(at)mindspring.com
Guest

Posted: Mon Sep 24, 2012 7:16 am Post subject: Melted wire

The wire to the STARTER solenoid is POWERED, not grounded.  The body of the starter solenoid is isolated from the coil and the starter power circuits.  One can unbolt the starter solenoid from the firewall, and so long as the jumper wire from the coil terminal to ground is maintained, it will function as it was intended.



This thread started about a MASTER solenoid wire failing, and somehow morphed into STARTER solenoid wiring discussion.



--Bob Steward



 	  Quote: 	
		  From: Rick Lindstrom 

I'm guessing here, without a wiring diagram in front of me, but wouldn't a poor mechanical ground to the body of the starter solenoid >result in all current going through the 18 ga. wire instead?

If so, that would overheat the wire for sure.

Rick

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