Mag’s Insulated Ground shield wire

[Mooney-Shiner]

I have one Insulated Ground shield wire that attached to the left mag on my 67F. It’s pretty flimsy connection and I would like to have it rebuilt.

is there a guidelines on how it supposed to look like? I didn’t see it in IPC or service manual.

 

 

[N201MKTurbo]

If you want to make it bullet proof, put a solder sleeve on it.

[N201MKTurbo]

[N201MKTurbo]

You can also replace the whole P lead back to the switch.

https://bogertaviation.com/products/p-leads-bendix-round-nut

[N201MKTurbo]

If the wire is long enough, you can resolder the center and shield back on the p lead connector. If it is too short, your only choice is replacing it.

The instructions for assembling the p lead connectors is usually found in the magneto service manual.

[PT20J]

Check the ignition switch end. If it’s grounded there, you don’t need to ground it at the mag end. In fact, shields are usually only grounded at one end so that no current can flow if the two ends are not at the same potential. Slick recommends grounding at the ignition switch, I believe.

[0TreeLemur]

On 6/26/2024 at 11:53 PM, N201MKTurbo said:

At first glance, these seem great.  However, I hear from my son who is in the instrumentation industry that these connectors have known reliability issues.  I personally would not use one of these on an airplane, especially in a location that experiences a lot of heat.

[N201MKTurbo]

8 minutes ago, 0TreeLemur said:

At first glance, these seem great.  However, I hear from my son who is in the instrumentation industry that these connectors have known reliability issues.  I personally would not use one of these on an airplane, especially in a location that experiences a lot of heat.

Strange, almost all avionics installs these days use tons of them. Garmin recommends them in their install manuals. If they are properly installed and inspected, meaning that you can see a clean solder flow to the ground wire and to the shield wire, I don't see how they can fail. Why do you think heat would affect them? do you think it gets hot enough to melt the solder? It is hard to imagine that would happen. and the heat shrink on them can withstand soldering temperatures, so I don't think normal engine compartment temperatures would negatively affect them. If your son is seeing failures, I suspect they are not being properly used.

[EricJ]

33 minutes ago, 0TreeLemur said:

At first glance, these seem great.  However, I hear from my son who is in the instrumentation industry that these connectors have known reliability issues.  I personally would not use one of these on an airplane, especially in a location that experiences a lot of heat.

Solder is generally frowned on for joints and pin connections, etc., since the end of the solder wick in the wire conductor creates a stress point.    These solder sleeves for shield grounding don't really do that, though, and they're used all over in avionics.   It's kind of the go-to method for grounding shields these days.

That said, I wouldn't use a solder sleeve for a wire splice, though, since it has the same issues as using solder for pins, etc.

[MikeOH]

A proper, gas-tight, crimp is a far better way to join wires for a long-term reliable connection.  Solder in a high vibration environment is less than ideal.

[jamesm]

All solder sleeve aren't created equal just like tools and most everything else. When I  use to work at a large commercial aircraft manufacture company in the PNW  during the late 80's. We had both solder sleeves (we called Zaps) and mechanical ferrules. Hardly ever used  the mechanical ferrules  style connection just to show you how to make one but that was about it maybe in high vibration area of the aircraft.   The solder sleeves that we used (Raychem if my memory is correct)  required gun that used an infrared heat source to melt solder sleeve and heat gun was not to be used. I believe that these solder sleeves were made to a certain specification and probably not the same ones  you can buy online someplace.  I have notice a quite a difference in quality in the various in solder sleeves from the cheap knock off versions from amazon and even different one that I have bought from reputable well known aviation source.

Just my observations,

James '67C

[EricJ]

30 minutes ago, MikeOH said:

A proper, gas-tight, crimp is a far better way to join wires for a long-term reliable connection.  Solder in a high vibration environment is less than ideal.

It's hard to crimp a shield connection.   I'm a fan of properly crimped connections for nearly everything else, though.

[PT20J]

I believe Raychem invented the solder sleeve. We used them on space-qualified high-reliability equipment in the 1970s. Part of the secret is that that amount of solder is controlled and encapsulated in the sleeves so it does not wick beyond the sleeve which provides strain relief. Properly installed, they are very reliable.

[Mooney-Shiner]

On 6/27/2024 at 11:59 AM, PT20J said:

Check the ignition switch end. If it’s grounded there, you don’t need to ground it at the mag end. In fact, shields are usually only grounded at one end so that no current can flow if the two ends are not at the same potential. Slick recommends grounding at the ignition switch, I believe.

Thank you! You are exactly right, the p-lead shielding is terminated at the Bendix 10-357200-1A ignition switch  with another connection to the body of the aircraft.

Thank you for the feedback, everyone. MS wins again!

[EricJ]

12 hours ago, Mooney-Shiner said:

Thank you! You are exactly right, the p-lead shielding is terminated at the Bendix 10-357200-1A ignition switch  with another connection to the body of the aircraft.

Thank you for the feedback, everyone. MS wins again!

Check the wiring diagram for your airplane.    There may be a Canon plug or other connector in the firewall that the p-leads pass through, and the shields will need to be grounded there on both sides of the firewall at that connector as well.   While grounding one end of a shield is definitely better electrically for reducing noise coupling into the signal conductor, in aviation applications the practice is usually to ground both ends, evidently for redundancy so if the ground on one end fails the shield is still effective.    The wiring diagram for my J shows the shield for the p-lead grounded on both ends of each segment on each side of the firewall.    As mentioned, it won't hurt to leave one end ungrounded and that's better electrically, but be aware that the wiring diagram shows a ground on each end.   This may be relevant if somebody else works on it and wants to ground both ends...which is fine and consistent with the wiring diagram.

[Mooney-Shiner]

20 hours ago, EricJ said:

Check the wiring diagram for your airplane.    There may be a Canon plug or other connector in the firewall that the p-leads pass through, and the shields will need to be grounded there on both sides of the firewall at that connector as well.   While grounding one end of a shield is definitely better electrically for reducing noise coupling into the signal conductor, in aviation applications the practice is usually to ground both ends, evidently for redundancy so if the ground on one end fails the shield is still effective.    The wiring diagram for my J shows the shield for the p-lead grounded on both ends of each segment on each side of the firewall.    As mentioned, it won't hurt to leave one end ungrounded and that's better electrically, but be aware that the wiring diagram shows a ground on each end.   This may be relevant if somebody else works on it and wants to ground both ends...which is fine and consistent with the wiring diagram.

Thank you for the help. 

Looks like my IPC asking for the grounding on one end (at the switch). 

[EricJ]

3 hours ago, Mooney-Shiner said:

Thank you for the help. 

Looks like my IPC asking for the grounding on one end (at the switch). 

And no firewall connector, so that makes it easier!

It says M20E on the side, does that apply to your F as well?

[Mooney-Shiner]

1 minute ago, EricJ said:

And no firewall connector, so that makes it easier!

It says M20E on the side, does that apply to your F as well?

It does. But we made another ground to the firewall