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MG Midget and Sprite Technical - Dielectric grease

Friendly garage gave me a tube of Dow Corning DC4 Compound.

He said it was good for electrical connections but I am not quite sure how to use it. I presume that as it is described as a waterproofing grease one smears it on the outside of a plug-in connector, taking care to keep it OFF the contact surfaces?
But maybe that is wrong and you use it quite the opposite way, smearing it ONTO the metal contacts to stop them corroding?

Any advice please - this is how DC describe it:

Silicone Compound - DC4
A smooth, silicone, grease-like material which maintains relatively constant consistency over operating temperature range. It has excellent dielectric properties and is also highly water repellant. It can be used as a filling or a coating to exclude moisture or prevent electronic leakage under damp conditions in electronic equipment. Also very handy to use as a lubricant when working with wiring.

What does dielectric mean?
Guy Weller

link below might help with the grease, I'm not the best to explain words so I'll leave that to your search engine

http://www.wisegeek.org/what-is-dielectric-grease.htm
Nigel Atkins

I've applied the stuff directly to connections and contacts for some time now, with no problems.

Cheers,

-:G:-
Gryf Ketcherside

quote from link - 'it can sometimes cause a connection to stop working if not all of the grease is pushed out of the way between the points of contact inside the connector'

you might be thinking of electrical contact grease that Bill always recommends - this might not be the right type but is used as an example explanation only - http://www.swantek.com/html/products/gre46103.htm

electric gets through the smallest of contacts sometimes

I've used coppergrease before to protect connections and make them easy to part without problems too but the proper stuff is available as electric contact grease
Nigel Atkins

http://www.dowcorning.com/applications/search/products/details.aspx?prod=01903128&type=prod
Lawrence Slater

Thanks all.

I had already done some searching on the net but even the manufactures info sheet seems contradictory. The underlying properties seem to be waterproof and insulating
which is why l was concerned about smearing it all over the contact surfaces ! And l read the words on the Wiki site about dialectic but didn't understand them.

Nigel. I have some of the stuff that Bill recommends. I just wasn't sure if this was basically the same thing in a bigger free tube.;-)
Guy Weller

Yes a dielectric material is an insulator. I have usually come across the term when referring to the separating insulating layer between the conductive plates in a capacitor.

So, it seems that its good to use where you don't want to create a stray conductive path, but need to protect from moisture. I recall using a silicone grease of this type around the distributor cap to body seal on my mini cooper. It may still be in the drawer somewhere, but I don't know what condition its in after all this time. I parted with the mini in about 1983! (Wish I hadn't now, but needed 4 door family transport then.)
Peter B

Thanks Peter,
What I used it for was on the insulated nose pieces of the coilpacks on my wife's Honda. The long insulated extension that pushes down to connect to the plugs way down deep in the engine. I was getting a very slight misfire which I had diagnosed as slight tracking up the surface of one of the the connectors. A smear of this grease seems to have cured it.

I was then considering where else I might use the stuff on the Sprite electrics. It seems I was right to check as I need to keep it away from the actual contact surfaces if its primarily an insulator.
Guy Weller

I've come across dielectric fluid in Electro Discharge Machining EDM. The dielectric fluid acts as an insulator between the tool electrode and the work electrode and also acts as a coolant and to flush the spark gap. I was at one time a EDM Setter.
Pete Ottewell


Silicon grease is used a lot on moving contacts
to help prevent arcing . A very fine film
is used on contacts in 440v equipment.
rehards pete k
P C Knightley

So now I am still confused!
Its an insulator so I wouldn't want a continuous layer between electrical contact surfaces.
But it is also a lubricant and prevents corrosion and arcing.
So maybe a very thin film is OK and wouldn't impede the current in the connection? Or is it better kept to the outside plastic outer housing of a connector?
Guy Weller

funny that I was just about to put whether it's clear to you or not after the contributions from the leccy boys

I'm sticking with my posts but I'm not a trained/qualified or gifted amateur electrician - just what I know I've got away with before not if it's technically correct either way
Nigel Atkins

To be honest Nigel, and I am not being "funny" but I wasn't even sure what you were saying! You included links, and talked about using copper ease and electrical contact grease. But no comment on the Dow Corning DC4 grease.
Guy Weller

fair enough, I can't see the problem with the posts but then I know what I mean and haven't communicated it to you

why not just test it out on a work bench test set up and decide for yourself
Nigel Atkins

Yes, I might try that, comparing the resistance of a well cleaned bullet connection with the same lathered in this compound.
I am now thinking that if the connection is clean to start with, and has a reasonably tight physical contact surface, then the grease will be squeezed out from between the actual metal connection surfaces. The excess will then fill the voids around it and the plug, and seal the contacts from water and atmospheric induced corrosion.
Guy Weller

yeah - that's what I quoted from the link

Dave wants help explaining what fast idle is on another thread, I think you could help as I'd over simplify it - thread called 'Confused idle'
Nigel Atkins

Guy
Yes. That's the way I understand it. But then I could be wrong - I frequently am-or so swmbo tells me.
Peter B

As I understand it a dielectric insulates but also enhances / makes possible induction by the nature of its constituent materials. (It helps electromagnetic induction but insulates the component parts so no direct electrical connectivity happens). So I think a dielectric is in for instance the coil where the high induced current or voltage (12v in lots out?) for the spark is made (capacitors use the same principal and have dialectrics in them I think). If the dielectric material did not enhance the induction but restricted it you would need more power in to get the same higher power out.
This fits with Pete's understanding below.

(I know I have mixed up lots of terminology; I am only trying to convey the idea here. If there is anyone that maintained or designed electrical machine tool control systems back in the day they would give the best answer as those old relays, crt screen starters, and strip light starters all used the principal of induction and therefore the component parts needed to be insulated well but not so well that induction between the parts could not happen). Where are the ex Physics teachers here?
Dave Squire (1500)

Hi guys,

While you are correct in thinking that getting grease between two contacts would interfere with the electrical flow, you are missing a key element of how electrical terminals mate with each other.

The terminal is designed to scratch its mate on insertion, and the surface contact at that scratch is where the electrical connection is made.

Tin plated terminals have a very thin layer of tin oxide on their surface, which is also an insulator, and so that scratch is necessary to get through that layer to make the successful connection. Tin is ideal for coating electrical terminals because it produces such a thin layer that it is real easy to get through.

However, in any electrical joint, the re-growth of that tin oxide layer will interfere with electrical flow, so an oxygen barrier is effective to protect the joint. The more exposed the joint is to water and water vapor the more this comes up as an issue.

So, even though dielectric grease is an insulator, the scratch of the terminal insertion pushes the grease away from the actual contact surface area, and the rest of the grease then seals and protects that important area from exposure to the elements which could cause it to become a poor connection in the future.



Norm
Norm Kerr

and having a tighter rather than looser terminal fit is better

I was going to put something like what Norm has put about the very small area of actual contact but didn't think I'd be as clear to understand

when you consider how the leccy still gets through some contacts and how few strands of wire are sometimes left complete or on contact on some connections there's a lot of leeway in some connections - obviously you want the best full connection you can get but it can be quite a way off that and still work
Nigel Atkins

A few years ago I was having intermittent problems with the left front turn signal on my '98 VW GTI. After cleaning the connection several times only to lose contact yet again, I finally cleaned it again, then filled the connector sockets with dielectric grease and reconnected it. I had no further issues after that.

And for what it's worth, I once did some restoration work on a large houseboat... a part of that project involved running wiring and installing small 12V and 24V halogen lights in the ceiling panels. We used Scotchlok connectors for all the unions in those circuits, as they were approved for marine use; basically, anywhere there was a propensity for corrosion. These connectors were filled with a grease of some sort. The Scotchlok literature states, "Factory inserted sealant insulates the connections, protects against corrosion, and seals out moisture." So they call it a sealant, but I assume it performs the same function as a dielectric grease. If anybody's interested, here's a link to some Scotchlok info: http://multimedia.3m.com/mws/mediawebserver?mwsId=sssss72sFWtTz8UuNy9gP8_sFWuRFWtsFWtsFWtsFssssss--&fn=ur2uy2ub2a_conn.pdf

Cheers,

-:G:-
Gryf Ketcherside

Older batteries used to vent hydrogen gas all over the place. The terminals would get covered in a powdery blue white substance because of this. With newer batteries, it shouldn't be such a problem, but it can still happen, and moisture in the air adds to the problem. Eventually the terminal and clamp are insulated from each other.

Adding an insulator in the form of a thin grease between the clamp and the terminal doesn't improve conductivity, but it does prevent corrosion. The theory is that the thin layer of grease that repels moisture and hydrogen gas, is better than a thick layer of insulation caused by corrosion.

A dielectric is an insulator as far as DC is concerned, and a conductor as far as AC is concerned. The difference between it and a straight insulator, is that it can be polarised. Hence it's use in capacitors to enhance the effects.

Quite why it's suggested to use a dielectric grease on battery terminals doesn't make sense. It's more use on high voltage applications because it doesn't breakdown with high voltages. So it's more useful to prevent corrosion under the rubber boot of the HT lead than on the battery terminals.

Taking Norms argument, if the terminals and clamps were perfectly smooth, then there would be no "gaps" for moisture or anything else to penetrate and create a problem. But the terminals and clamps are often a poor fit. So moisture does get in, and insulating corrosion builds up.

People used to use Vaseline -- petroleum jelly. It does the same job of repelling water and hydrogen gas, but it's way cheaper than dielectric grease. One theory is that tiny particles of copper or aluminium are caught up in the Vaseline, and when you tighten the clamp these ensure that there is a very low resistant path while the Vaseline makes the joint air and water proof.

Much better would be copper grease as Nigel suggested. It has excellent conductive properties.

Personally I think it defies logic to smear electrical terminals with an insulating grease BEFORE clamping.

Imho, it's better to clean and smooth the terminals prior to clamping, then tighten them up good and tight. THEN apply a layer of grease to keep the nasties out.

Myself, I've never used a grease of any kind on the battery terminals. I just make sure they are in good clean condition before clamping them, and I've never had a problem with poor contacts.
Lawrence Slater

modern battery posts don't need protecting as such now they say

I didn't know copperease had excellent conductive properties, where did you find this info please, Bill almost persuaded me that I'd got it wrong to use it on batteries but then I remembered using it years ago

the ac or dc bit makes some sense to the info given
Nigel Atkins

Physical properties of Copper Grease
Appearance A copper coloured aerosol grease
pH Not applicable
Specific Gravity About 1.00 [Base]
Non Volatiles % m/m 30 - 40
Active Content % m/m 45 - 55
Flammability Extremely flammable, flash point below -20°C
Composition Data, descriptive A suspension of copper, graphite and hydrocarbon solvent in a
solvent refined mineral oil, dispersed in a hydrocarbon
propellant
Anti-seize temperature range -18 to +1,100°C

"Electrical conductivity Excellent" Which is not surprising really when you consider it contains pure copper embeded in grease.

http://www.copper-grease.com/copper-grease-technical.html
Lawrence Slater

I use the stuff on spark plug wires to the plugs and the cap... battrey cables, starter and alt cables, light bulbs weather there head lights or dash lights, as well as ground connections esp those ones that like to rust and trap dirt... the horns and running lights with there contacts inside the fenders is a great place for that stuff

I think another great plus would be bullet connectors as well... ive cut out all my bullet connectors and welded the wires togather so I cant say for a fact how well this stuff would be on the bullet connectors

basically as it says. where water and corrosion can be an issue...thin application, a little goes along way

prop
Prop and the Blackhole Midget

Another simple question turns out to be an interesting discussion !
Guy Weller

cheers Lawrence, I thought the oil/grease the copper is suspended in might be less conductive than the copper

one downside of coppergrease is that a tiny spot of it can cover all your clothes, worse than Waxoyl
Nigel Atkins

Best put it on naked then Nigel. lol.
Lawrence Slater

even I felt instantly sick when I saw that remark
Nigel Atkins

Well Nigel, that's what you get for looking in a mirror at your age. I cracked all mine years ago. :)
Lawrence Slater

we haven't got a mirror that does more than partial coverage now, funny as I remember the mirrors being wider, must have remembered wrong again
Nigel Atkins

This thread was discussed between 14/03/2013 and 16/03/2013

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