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When / where to use dielectric grease?

 
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blues750



Joined: 06 Jun 2015
Posts: 46

PostPosted: Tue Jan 01, 2019 9:49 am    Post subject: When / where to use dielectric grease? Reply with quote

Recently, while inspecting the engine compartment after some routine maintenance, I noted a section of "browned and crispy" wire insulation. This particular wire was one of the 3 phase wires which come from the 30A PMA associated with the engine. The brown and crispy portion was at the back of a plastic 6 blade connector half where crimped 1/4 female spade connectors are inserted to mate with the Regulator/Rectifier. The crimps are good, all spades firmly seated into the shell, though the spade (associated with the browned wire) location on the shell also show sign of getting too hot. But only at the one spade connection. Overheating due to high resistance is the only thing that comes to mind. I did apply dielectric grease to these particular spades to help them fully mate and as a corrosion/moisture preventative. I do this routinely on older cars up here in the Northeast with no issues. Could this be a problem? I typically draw 18-22 amps load while flying but when topping off the batteries will draw closer to 30 amps for 10-15 minutes of flying if the batteries have been drawn down for extended times during non flight activity. Note that the output from the R/R looked fine but they are a larger gauge wire. (12ga versus 14ga of the 3 phase wires into the R/R) Rather lengthy problem description for what appear to be an overheated wire, open for all thoughts or ideas. The only one I can come up with is poor connection / high resistance, though not sure of the mechanism. Thanks, Happy New Year to all!!

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gilles.thesee(at)free.fr
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PostPosted: Tue Jan 01, 2019 10:34 am    Post subject: When / where to use dielectric grease? Reply with quote

Le 01/01/2019 à 18:49, blues750 a écrit :
Quote:
I did apply dielectric grease to these particular spades to help them fully mate and as a corrosion/moisture preventative. I do this routinely on older cars up here in the Northeast with no issues. Could this be a problem? I routinely draw 18-22 amps while flying but when topp!

Hello,

Just to mention that "dielectric" means "insulating".
Don't know if this is a problem, but gas tight metal to metal is key.
Quote:
Rather lengthy problem description for what appear to be an overheated wire, open for all thoughts or ideas. The only one I can come up with is poor connection, though not sure of the mechanism.


We have had the same issue with some wires off the voltage regulator
connector. We replaced the wires and spade terminal, paying attention to
the quality of the crimp.

Happy New Year !
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr


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blues750



Joined: 06 Jun 2015
Posts: 46

PostPosted: Tue Jan 01, 2019 12:54 pm    Post subject: Re: When / where to use dielectric grease? Reply with quote

Gilles, I think you may be on to something! I likely "gobbed" on too much dielectric grease and prevented a good electrical connection as the grease heated up and spread over the metal to metal connections. My plan is to clean up and replace the connections, reassemble with no dielectric grease! Thanks for the reply. Cheers! Dave

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user9253



Joined: 28 Mar 2008
Posts: 1385
Location: Riley TWP Michigan

PostPosted: Tue Jan 01, 2019 5:45 pm    Post subject: Re: When / where to use dielectric grease? Reply with quote

Most common grease is dielectric. Its use should not cause a problem. A properly crimped joint forces all grease out from between the metals. I have coated automotive battery terminals with grease and the vehicle still starts fine. The problem is due to a bad crimp.

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BARRY CHECK 6



Joined: 15 Mar 2011
Posts: 739

PostPosted: Tue Jan 01, 2019 6:42 pm    Post subject: When / where to use dielectric grease? Reply with quote

Joe & Gaggle:
Dielectric Grease is Silicon based all 100% synthetic.  Automotive greases, and oils for that matter which are NOT 100% synthetic, and there should not be any 100% synthetics.  [Yes, I know they advertise 100% synthetic but unless something has changed no, engine oil is 100% synthetic.]  Petroleum Oils & Greases will trap moisture!  Just like the water that is found in your engine oil.  The axle grease on the battery terminals will work for a long, long time.  It is just not the best way to attack the issue.  Do you really need to go the route of the Ultimate Silicon Dielectric Grease path?  Well, not for a automotive battery terminal.  BUT!  For the whole $1.00 for a Permatex packet - YES - That is the way to go.  And when using the dielectric grease on terminals of different metals:- copper, silver, gold, tin, solder and mixtures of them, why take a chance of corrosion.  After all, we know automotive oils do become acidic!
The posted question on WHY use dielectric grease especially since the term dielectric means Non-Conductive.  GREAT QUESTION!
Slop on the dielectric grease to the point of just becoming sloppy.
THEN complete the connection...  Fast-On connectors just slide them together.  As they push together the CONTACT POINTS will make both a mechanical and an electrical contact pushing the dielectric grease out of the way.  YET!  The grease will be in enough places to create a oxygen and moisture barrier.  DON'T think you solved the problem for ALL time.  The dielectric grease will migrate and become washed off, by YOU - When you wash the plane or use engine de-greasers or fly through rain.  Use it...  Then re-use it when you cannot see the nice coating you original put on.  
Joe - You said it!  BAD CRIMP!  Yup, I agree 1,000 %.  Wrong size terminal.  Wrong size wire for the terminal. Wrong type wire used.  Wrong TOOL used for the crimp.  
Little Trick:  One job that I worked on where the terminals were in a particularly difficult location to get at for inspection or repair AND the piece of equipment was was on the deck of an Aircraft Carrier for extended periods of time.  The requirement was to:
1 - Put Dielectric Grease - IN - the terminal BEFORE CRIMPING.
2 - Dip the wire into Dielectric Grease.
3 - Assemble and then CRIMP.
There were no issues of a resistive connection.
Yes, I do believe in dielectric grease.
And, it's great for keeping your hair in place on dry staticky days.


Barry
On Tue, Jan 1, 2019 at 8:50 PM user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:

Quote:
--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

Most common grease is dielectric.  Its use should not cause a problem.  A properly crimped joint forces all grease out from between the metals.  I have coated automotive battery terminals with grease and the vehicle still starts fine.  The problem is due to a bad crimp.

--------
Joe Gores




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blues750



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PostPosted: Wed Jan 02, 2019 4:38 am    Post subject: Re: When / where to use dielectric grease? Reply with quote

Here are a few pics of the connector in case anything can be determined by the pic. Will post pics of crimps when I remove wires and assess. Thanks for the input all. Dave

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blues750



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PostPosted: Wed Jan 02, 2019 4:36 pm    Post subject: Re: When / where to use dielectric grease? Reply with quote

OK, had a chance to remove the wires from the connector shell. I would like to think all my crimps looked like the "good looking crimp and wire" I cannot imagine I would have proceeded without having them otherwise. But... the other wires look pretty p*ss poor! The bare wire had hardened insulation which I peeled off to inspect wire condition. Seems like a lot of corrosion for such a "young" connection! In reading Bob's related reply, I can easily be lead to believe that those (my) crimps are in the "neophyte" category for these particular terminals. I cannot recall the crimp tool name I used, but it is oe I purchased from SteinAir expressedly for doing open barrel crimps. Thoughts, insights, and opinions??

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sha664817



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PostPosted: Thu Jan 24, 2019 3:25 am    Post subject: Re: When / where to use dielectric grease? Reply with quote

There's a lot of chatter about the use of dielectric grease. Permeate suggests that Dielectric Tune-Up Grease is a good barrier to oxidation at plugs, connectors and terminals. There are some online comments at forums that say not to place dielectric grease on connector pins.

I've gone to the Permeate site, and the information is vague:

"Protects electrical connections and wiring from salt, dirt and corrosion. Extends the life of bulb sockets. Prevents voltage leakage around any electrical connection. Also prevents spark plugs from fusing to boots. Required for modern high energy ignition systems."

Directions for Connectors: 1. Make sure ignition system is off. 2. Clean surface with Permeate Contact Cleaner. 3. Coat both parts of terminal contact with Dielectric Grease. 4. Reassemble, maintaining metal-to-metal contact.

In the PDF, Permatex cites uses for the Permatex Dielectric Tune-Up Grease:

TYPICAL APPLICATIONS

• Spark plug boots

• Distributor cap nipples

• Battery terminals

• Ignition coil connectors

• Headlamp connectors

• Trailer electrical connectors

The "metal-to-metal contact" reference may create suspicion for some about "Dielectric Tune-Up Grease". I've used this product for years around tune-up work without reservation. I searched around and found an engineer's assessment of dielectric grease that suggests Permatex Dielectric Tune-Up Grease should work well on a variety of pin connector materials without creating any kind of resistance or barrier to current flow. This commentary is worth reading: http://www.w8ji.com/...tive_grease.htm, the author seems well informed, experienced, and he uses a scientific approach. According to the engineer, metal-to-metal pin contact should result if pins are clean and not tarnished, with or without dielectric grease on the pins.

It's realistic to presume that the degree of conductivity is governed by the tension of the pin and socket fit, not whether we use dielectric grease. Whether or not you use the dielectric grease, I would use a quality electrical contact cleaner to get rid of the oozing material at your PCM plug and terminals. Make sure you flush out all residue and allow complete evaporation to prevent dilution of remaining grease or any issues with spark arc hazards. I would at least place dielectric grease on connector lips to act as an effective moisture and oxidation barrier.


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PostPosted: Fri Jan 25, 2019 10:46 pm    Post subject: When / where to use dielectric grease? Reply with quote

I can only comment from my experience on boats and docks. I have seen
less corrosion problems on connections treated with dielectric grease.
The difference can be seen in a matter of a couple of seasons,
especially on ones that are removed and replaced frequently, such as
removable anchor lights and cigar lighter type connectors. Admitted
these are not high buck sealed connections designed for the harsh
maritime environment, but using grease changes them from problematic
designs to being reliable connectors.

Raymond Julian
Kettle River, MN

The things we admire in men, kindness and generosity, openness, honesty,
understanding and feeling are the concomitants of failure in our system.
And those traits we detest, sharpness, greed, acquisitiveness, meanness,
egotism and self-interest are the traits of success. And while men
admire the quality of the first they love the produce of the second.
-John Steinbeck, novelist, Nobel laureate (1902-1968)

On 1/25/19 12:03 PM, Robert L. Nuckolls, III wrote:
Quote:
At 05:26 AM 1/24/2019, you wrote:
>
>
> There's a lot of chatter about the use of dielectric grease. Permeate
> suggests that Dielectric Tune-Up Grease is a good barrier to oxidation
> at plugs, connectors and terminals. There are some online comments at
> forums that say not to place dielectric grease on connector pins.
>
> I've gone to the Permeate site, and the information is vague:
>
> "Protects electrical connections and wiring from salt, dirt and
> corrosion. Extends the life of bulb sockets. Prevents voltage leakage
> around any electrical connection. Also prevents spark plugs from
> fusing to boots. Required for modern high energy ignition systems."
>
> Directions for Connectors: 1. Make sure ignition system is off. 2.
> Clean surface with Permeate Contact Cleaner. 3. Coat both parts of
> terminal contact with Dielectric Grease. 4. Reassemble, maintaining
> metal-to-metal contact.
>
> In the PDF, Permatex cites uses for the Permatex Dielectric Tune-Up
> Grease:
>
> TYPICAL APPLICATIONS
>
> • Spark plug boots
>
> • Distributor cap nipples
>
> • Battery terminals
>
> • Ignition coil connectors
>
> • Headlamp connectors
>
> • Trailer electrical connectors

Dielectric greases and coatings are proven prophylactics
that ward off the effects of adverse environments for
which the potential 'victim' is ill-equipped to
manage on its own.

Borrowing from the assertions of another competent
observer of really big numbers, let us consider what
must be 'billions and billions' of mated conductors
in connectors that have performed over the LIFETIMES
of the target technology with no 'extra' protection
squeezed out of a tube or brushed on from a bottle.

Does this mean that such products have no useful
place? Not at all. My FIRST experience with dielectric
grease moisture protection was 175' up on
a tower where the boss told me that filling the
mated coax connectors with DC4 before assembly
had a demonstrated value for shielding connectors
exposed to Kansas climate way up in the air.

Over the years, I have had occasion to open factory
assembled connectors that were obviously offered
the benefits of protection above and beyond those
offered by the enclosure. This includes lamp sockets
on tail and back-up lights, marker lights and
yes, trailer connectors.

These instances were most common on fixtures
especially exposed to splash or run-down. When
refurbishing equipment that succumbed to
contamination induced corrosion, the
'rule of thumb' called for protecting
the replacement hardware with a good
dielectric grease. But it was also a good
idea to see if some gasket had failed
allowing ingress of moisture.

Emacs!

In years since, designers for electrical
connectors improved designs to improve
performance in harsh environments.
The moisture seal bellows on this
connector is one example.

Emacs!

It's been a long time since I've opened
a connector that contained any previously
applied protection against moisture.

It stands to reason that suppliers of
such products want to sell as much as
the market will purchase. The marketing
problem is that it's seldom necessary/beneficial.

The only time I've used the stuff is
to provide an extra layer of protection
for components that replaced victims
of moisture damage . . . or selected
instances of extra-ordinary risk . . .
like difficult-to-access 175' up on a tower.

The short story is that these products
are best applied during replacement
of parts that have succumbed to moisture
effects. But when such damage is
discovered, be sure to evaluate
the circumstances of the failure.
Was the connector a poor choice to
begin with? Was it subjected to
environmental stresses outside original
design goals? Does a sealing feature of
the enclosure need refurbishment?

I have a 4oz tube of DC4 that is probably
40 years old and barely shows signs of having
been squeezed. Dielectric grease is
a band-aid on a marginal design.

Bob . . .



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Kellym



Joined: 10 Jan 2006
Posts: 1589
Location: Sun Lakes AZ

PostPosted: Sat Jan 26, 2019 3:48 pm    Post subject: When / where to use dielectric grease? Reply with quote

That must be an old picture of DM AFB. I believe one of the arms
treaties required the tails chopped off.

On 1/26/2019 10:34 AM, Robert L. Nuckolls, III wrote:
Quote:
At 12:45 AM 1/26/2019, you wrote:
>
There is a tank on the beach of
Culebra Island, PR that has been sitting
there since WWII. Dug around through
the interior a few years back.

Emacs!

The salt water has literally dissolved
major cross sections of steel. On the
other hand, one could have stored this
machine next to a tenant of the Davis
Monthan 'bone yard' . .


Emacs!

. . . and the machine might well be
operational with nothing more than some
fuel and a grease job.


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