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Electrical connections again - The inspection
Posted to HD/Fleet Forum on 5/1/2013 50 Replies

Dean was kind enough to send me his wiring connection from the post here:

I inspected it, sourced some solder seal connectors did a regular solder joint and did some comparisons with pictures. Here are the results.

At first glance it looks like the joint Dean did looks to be ok. Looking closer shows some serious flaws in the solder joint. A good solder joint will be shiny after completion, the solder will have flowed freely through the strands of wire and filled in the gaps. The solder seal connection left a dull appearance with lumps and poor flow. Very characteristic of a cold joint where the solder was hot enough but the surface was not hot enough for adhesion and flow. [Comparison] Any tugging on the wires at all and the solder would peel off the wires. Proper joints will not do that. [Teardown]

Next I tried several temperature ranges with the solder seal connections and a propane torch to see what the results would be. Would it be possible to get a good solder joint? I used a 16 gauge wire for the benefit of better wire heating for proper adhesion. Thicker wires take more heat.

The first try resulted in a job very similar to what was listed earlier. A clean shrink and the solder ring collapsed into the wire. [Good Shrink] A job most techs would be proud of. After cutting away the heat shrink I found this [Good Shrink 2] [Good Shrink 3] While the solder did indeed melt and get squished into the wire by the shrinking heat shrink the solder did not penetrate the joint or flow well. I tried this several times with similar results each time.

Next was to use less heat. [Cold Shrink] The heat shrink did its job by shrinking down and sealing to the wire. The problem is it sealed before the solder ring collapsed leaving an air pocket. The solder did eventually melt but there was nothing to push it into the wire let alone ability of the wire to get hot enough for adhesion. [Cold Shrink 2] The result was a miserable failure.

Last I tried to get the joint hot enough for the solder to flow properly. This can be successfully done if you don't care about the seal. [Hot Shrink] Heat has to be kept on the joint after the heat shrink has shrunk and the solder ring collapsed. Otherwise the wire won't get hot enough for adhesion and flow. [Hot Shrink 2] You can see where there was good flow and it is shiny on the left side. The right side was too cold, is dull and didn't flow well. not much of a temperature difference side to side but it was enough.

I have concluded as before that the solder seal connectors are cold solder joints which hold the wires together for rigidity and nothing more. Although there are probably a lot of applications where they will work well, such as trailer lighting, I would never use them on a circuit where voltage drop is a critical issue, such as throttle actuator circuits. Definitely better than a scotch lock but there are much better options such as proper crimping and adhesive lined heat shrink tubing or solder and adhesive lined heat shrink tubing.

Andrew from Utah

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