Dielectric Grease and none friction contacts ?

Discussion in 'General Electronics Chat' started by HonesTisThePathToLife, Dec 6, 2018 at 9:29 PM.

  1. HonesTisThePathToLife

    Thread Starter New Member

    Nov 25, 2018
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    Hello I could really use some detailed advise I`ve been reading a lot of misinformation from people guessing at the answer due to having no education in this technical field.

    1st I will explain the intended purpose, My vehicle distributor cap and rotor is worn I sanded the contacts inside to buy some time as it was acting up but for the new parts this time I was thinking of using some 3m silicone paste dielectric grease I bought for other reasons...

    I`ve read to use sparingly and not glob it on but very thin layer over the contact points.

    The question is since these are none friction contact points can it still be used sparingly ?
    I say sparingly as I have read globs can cause heat to build up . ?

    I have another question but to keep this thread clean I will save it for when I get a clear answer on the 1st :]

    Please keep in mind I do not have an education in the field and only do simple wiring I`m just starting to get curious about capacitors and circuits.

    Thank you in advance for your time and have a great day !
     
  2. wayneh

    Expert

    Sep 9, 2010
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    Are you talking about the contacts inside the cap, the ones that transfer spark from the rotor to the plug wires on the outside? If so, I wouldn’t bother with the grease. Your cap probably doesn’t enough life left in it to worry about additional corrosion.
     
  3. Sensacell

    Moderator

    Jun 19, 2012
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    Bad idea.

    The grease will burn from the high voltage sparks, creating carbon tracks that could stop the ignition from working.
    The inside of a distributor cap should be clean and dry.
     
  4. HonesTisThePathToLife

    Thread Starter New Member

    Nov 25, 2018
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    Thank you,

    is there nothing that would work to create better more superior conductivity and less arching damage...? The contact points in the cap are all burnt and chewed only on one side of them all, resembles someone taking a file to just a corner of each the contact points...
     
  5. Sensacell

    Moderator

    Jun 19, 2012
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    Its a rotary spark gap, not a contact switch.

    Gaps should be small with sharp edges.
    Replace the cap and rotor.
     
    wayneh likes this.
  6. MrAl

    AAC Fanatic!

    Jun 17, 2014
    5,341
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    Hello there,

    It is a common misconception that dielectric grease creates better conduction. It does not. It's actually an insulator.
    The reason it is used is to keep an already clean contact from oxidizing from normal exposure to moisture. This means that the contacts have to be clean before application if you want to keep them clean over some time.

    For a distributor however i dont think it would do much or would have a negative effect due to the arcing.
    The main problems in distributors i think is distance, where the rotor does not come close enough to the plug wire connections inside and so as it gets farther and farther away it means a less energy spark. Since di grease does not improve conductivity, it wont help at all but would more likely make the situation worse, and as it breaks down over time it would get even worse.

    Low voltage connections are fine as long as they are clean before the application.
     
    MaxHeadRoom likes this.
  7. LesJones

    Well-Known Member

    Jan 8, 2017
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    I tink a more likly problem is that the insulation of the distibuter is braking down and shorting out the high voltage. If you clean the inside and
    outside of the distributer and inspect it carfully I think you will find a track mark where the plastic has been turned to carbon. I think this is more likely to be on the inside. It was probably initialy caused by the high voltage being conducted by moisture on the surface. If this is the problem then you mau be able to remove the carbon track with sandpaper as a temporary fix. A coat of epoxy resin over the sanded area may be more permanent. I have just re read your post and realise that you have a new distributer. I agree with all the oter comments about not using grease.

    Les.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I agree with the last sentence, but as noted by others, silicone grease is used as an insulator typically used to prevent moisture ingress etc in spark plug rubber caps/boots.
    Max.
     
  9. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    And to attempt to keep the rubber of the boot from bonding to the plug ceramic overtime. This is the reason the engineers gave me when working where we made both the boots and spark plug wires.
     
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  10. HonesTisThePathToLife

    Thread Starter New Member

    Nov 25, 2018
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    I found this helpful comment online as other searches came up leaving me unsure...
    Quote from Youtube comment : Travis Pratt
    6 months ago
    They’re idiots because people never explain to them, dielectric grease is an insulator, but it also improves the connection when on two metal surfaces because little protected, free from corrosion divots form within the grease that conduct electricity much better than an oxidized or otherwise unprotected connection surface. Dielectric means it can be polarized by electricity, which basically means it doesn’t conduct electricity but moves out of the way on a molecular level when electricity passes through it. If your contacts would conduct electricity as they are, dielectric grease can only improve that connection, and more importantly protect it from naturally degrading from use. When someone says “dielectric grease is an insulator” in the context of using it on connectors, they don’t know what they’re talking about.

    I`m hoping to get another insightful comment like the above, I`m not sold on the polarized grease getting burned off as it is used in capacitors or so I have read, but I`m unsure of the amps in the 12 -14 volt arch so I cannot yet even begin to guess....

    If anyone can give educated real life expertise and not you best guess that is why I am here, Thank you for your time...
     
  11. wayneh

    Expert

    Sep 9, 2010
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    The impedance across the spark gap can only be degraded by adding something on top of the conductors. The only redeeming factor is anti corrosion, but I don’t think that’s worth the risk of degraded spark and might lead to worse problems than a little natural corrosion.

    People have been using naked metal inside distributor caps for decades and I’ve never seen a recommendation from a reputable source to do anything else.
     
    shortbus likes this.
  12. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    What you missed in that comment and I'm thinking most comments is the dielectric grease is used in metal to metal contact. Like a connector. The contacts inside a distributor aren't metal to metal, even when new there is a pretty big gap. If there was no gap the rotor couldn't turn inside the cap, and if the gap was smaller, every distributor, rotor and cap would need to be "perfect", no out of roundness no run out of any of the parts. In the real world this isn't possible.
     
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