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Thread: Heat shrink tubing- weather tight seal

  1. #1
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    Heat shrink tubing- weather tight seal

    I'm working on a engine harness and after much reading of debates between 'proper' crimping and soldering I decided to do a little of both throughout the harness. Some what of an test really to see how both hold up. Anyways after crimping some non insulated connectors to my wires, I was going to buy some adhesive lined heat shrink tubing but I have a ***** ton of plain heat shrink tubing laying around that I usually use for inside car wiring etc. Some of the wires I crimped will be under the hood so I want a nice water proof seal. I was wondering if there was a good glue that would not corrode or damage the crimped connector or wiring?

    Basically is there an glue I can apply to the un-insulated butt connector and the small amount of exposed wire and then slip an regular heat shrink tube over it and shrink it, let the glue dry and be water tight just like adhesive lined heat shrink?

    Some of these wires are for the ignition coils so using a glue that would interfere with conductivity would be my concern.

  2. #2
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    A normal hot glue gun works great, just don't think about getting them apart again. I used it for butt connections on my headlamp LEDs.

  3. #3
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    I was trained that the BEST connection you can get is a connection that is first crimped to make the best conductive connection then soldered to get the best mechanical connection. By crimping then soldering you still maintain your solid connection from the copper in the wire to the connector. The solder just solidifies the loose stuff.

    As to a sealant. The easiest to use is silicon but make sure it is non conductive. You can work the silicon with your fingers and get it over the connector then slide the heat shrink over the top of it making sure you have a little sticking out of each end then heat up the tubing and you should be all set. If your heat shrink is black you may like the results of using black silicon. Much easier to work with than hot glue and will last much longer in the weather. Not to mention silicon is generally used by the manufacturers when they do something they want sealed like that.

  4. #4
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    Are talking about a dielectric silicone grease? Or a silicone glue?

    Maybe use this?

    Permatex 81158 Black Silicone Adhesive Sealant

    http://www.amazon.com/Permatex-81158...=silicone+glue
    Last edited by Rell; 10-26-2012 at 03:30 PM.

  5. #5
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    Quote Originally Posted by redheadedrod View Post
    ...first crimped to make the best conductive connection then soldered to get the best mechanical connection.
    That should be the other way around, but I reckon that is what you meant.

    For the benefit of others, solder is NOT a strong mechanical bond - it includes soft metals like lead. But it does form a great conductive bond - both electrical & heat (except across dry solder joints).


    And though I often see "solder first, then crimp", it should be crimp first, then solder.
    Get the mechanical bonding first, then fill the gaps with conductive solder. (Why crush the fill afterwards - especially if to gain mechanical strength?)



    FYI - though soldered joints are often considered essential, I rarely do it in my vehicle(s). Sometimes that's thru consideration of the negative heating impacts (insulation degradation etc), but more often due to the inconvenience, or the "temporary" nature of such connections.
    As to the temporaries, it is amazing how reliable they have been - whether HU harness plug wire wrappings, or thin crocodile-clipped jumper wires to connect the engine bay's window washer bottle in a rally -cum- street car (for 3 years!).
    I have had more trouble with standard plug & socket connections going bad (after several years of use).
    But ANY intermittent or bad connection is a pain. I stay aware of what connections I have merely wire-wrapped and what failure means. If inaccessible or too risky, I'll crimp or solder.
    BTW - many auto and electronic connections are merely crimped and they will last a lifetime. However they may use "proper" crimping tools and not cheap imitations or simple copies.
    Last edited by OldSpark; 10-26-2012 at 09:22 PM.

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    Quote Originally Posted by OldSpark View Post
    That should be the other way around, but I reckon that is what you meant.

    For the benefit of others, solder is NOT a strong mechanical bond - it includes soft metals like lead. But it does form a great conductive bond - both electrical & heat (except across dry solder joints).


    And though I often see "solder first, then crimp", it should be crimp first, then solder.
    Get the mechanical bonding first, then fill the gaps with conductive solder. (Why crush the fill afterwards - especially if to gain mechanical strength?)
    I will explain my answer further...

    Crimp first... This gives you a good connection between the Butt connector material and the Copper in the wire.

    Soldering it DOES add mechanical strength.. It does this by bonding the wire to the butt connector so it does not move around. Although the solder may not be that strong it bonds the wires together with the connector and makes it very strong. If you wiggle wires back and forth in a crimped connector that isn't crimped perfect you can work the wires out and possibly break off single wires. By Soldering the wires to the connector you are removing this flexing of individual strands and bonding any loose wire to the connector and to other pieces of wire.

    The strongest connection is two stranded wires soldered together because they are bonded together within the solder. However solder is not a very good conductor when compared to copper so just soldering a splice can add resistance to the circuit that you don't want and need. Thus the reason for crimping the connector then soldering it... The best over all connection in an automotive use when using stranded wires.

    To seal the connectors you may use liquid electrical tape in place of the above mentioned silicon but use it the same way. I just did this on my truck but wrapped the wire in regular electrical tape after the liquid stuff dried.

    Also I will agree with Oldspark that if you crimp the connectors properly you should not need to solder anything but few people can do this perfectly even with the right equipment. If you solder the crimp after the fact it is an easy insurance..

    Ps... Originally Solder was made of Tin and Lead and is best for conductivity but most places want you to use lead free solder now so you don't poison yourself.. And lead free solder of course doesn't have any lead in it...

    For more information about solder feel free to go here...
    http://en.wikipedia.org/wiki/Solder

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    Your fist line was exactly what I was trying to convey. The point I was trying to make that wrt each tool's priorities, solder's is conduction integrity.

    Meanwhile though crimping can give good and long-term reliable conductivity, it's most important strength is - pun unintended - its mechanical strength.


    I doubt that you'd find texts telling you to solder crimps for the prime reason of adding mechanical strength.
    Nor crimpers telling you to merely solder and NOT crimp (since solder is stronger than crimping - not).


    I'm not saying that solder doesn't add strength, just that its MAIN reason is electrical conductivity - it prevents oxides etc forming between the mechanically bonded metals.
    Also that oft advise is NOT to rely on the solder alone for mechanical strength - that it not its strength. (Hence crimp first, then solder if desired - but don't solder and then crimp if that's an option.)
    Likewise firm crimps and even bolted joints can corrode and fail to conduct, or maybe even semi-conduct.
    However there are many crimp-only connections that are still fine after decades of use. This includes vehicle "pin to wire" connections that haven't had any conformal or other protection added despite being in engine bays or underneath etc.



    As to solder, privately I haven't used lead free stuff. But I am as mad as a hatter.

  8. #8
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    People please, lets not turn this into a discussion of soldering and crimping lol.

    Guess I should have left all that out of the first post. Question at hand was "is there an glue I can apply to the un-insulated butt connector and then slip an regular heat shrink tube over it and shrink it, let the glue dry and be water tight just like adhesive lined heat shrink?"

    I looked at the liquid electrical tape stuff but never thought much of it, I'll see what I can find out about it. Maybe I'll apply some of that over the connection and add some heat shrink over it and call it done.

  9. #9
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    Apologies - I wanted to correct a not uncommon understanding.
    But I also thought I was addressing your concern. Maybe a bit too indirectly...

    I'd question the need to seal a connector. I find that normal heatshrink is usually fine. Sometimes I might spray with Inox, or a silicon spray.
    I'll use Silastic type silicons like your linked Permatex for grommet fills etc, but rarely connectors. (Some can be corrosive. And future repairs to siliconed joints can be difficult.)
    I can imagine siliconing the ends of heatshrink that I have used to cover a join as that can be repeated if reworked.
    But connectors are there for connecting. If not, they should be replaced with straight-thru wiring, ie one-piece else wrapped, soldered & insulated (heatshrinked) joins.
    And I don't think I'd ever seal an electrical joint that didn't involve chemical bonding like solder or fusing.

  10. #10
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    Why not use some heat shink butt connectors? http://shop.genuinedealz.com/Marine%...Butt%20Splice/

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