Word to the Wise: Don't Solder Your Crimps - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 14 (permalink) Old 07-08-2019, 12:12 PM Thread Starter
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Word to the Wise: Don't Solder Your Crimps

So I'm humming along on my freshly-completed 2001 Bonneville custom, and suddenly when I hit a couple big bumps the engine goes dead. Pull over, try to start, the starter turns powerfully but no ignition. Try the old "screwdriver in the sparkplug wire" trick and sure enough, no spark.

Luckily I was near my house, so I'm able to push it there and pull open the electronics compartment. After a lot of trial and error, I find that one of the dozen ground wires that is screwed into the common ground terminal has broken at the ring-connector. (Difficult to diagnose because the break was invisible - it was inside a length of shrink tubing.)

Problem was that as I crimped mini-ring connectors to each wire, in an attempt to "overbuild" everything, I had soldered the connection and then added shrink tubing. Unfortunately the solder had wicked up into the wire and created a brittle section just where the wire met the connector, and then when I angled the connectors into the ground terminal, the bending weakened the brittle part enough that a few vibrations and bumps caused the wire to break at the connection.

Lesson is, do your crimps right, using the correct crimping tool for the wire and connector (you don't want to pinch it too tight or too loose), and then go with that - no solder. Even adding shrink tubing is a mixed bag: it adds some stress relief, but it hides the connection and you won't see a problem if it goes bad.
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post #2 of 14 (permalink) Old 07-08-2019, 01:28 PM
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Shrink tubing isnt really as necessary on ground cables as on leads either.
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post #3 of 14 (permalink) Old 07-08-2019, 01:38 PM
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That's a good point. A crimped connection should be air-tight and very much like a cold weld. Attempt to solder it will not improve the electrical connection but will likely require so much heat as to cause the insulation on the wire to not only melt but also wick into the wire. This eventually will create gaps between the conductors which wick and hold moisture and encourages corrosion, worst yet, up inside of the wire jacket where it is difficult to find. All of this with no benefit in electrical performance.

So crimp it right and leave it alone. No need for heat, heat shrink, or soldering if you have chosen the right crimp-on connectors and crimp tool.
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post #4 of 14 (permalink) Old 07-08-2019, 01:55 PM
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Curious to hear this. My Dad has always said soldering crimped connectors on engines and vehicles in general is a bad idea b/c of vibrations leading to breakage as you describe. That is why you never see OEM vehicle wiring with solder connections. But I admit I've done it myself and have not had breakages. Matter of luck more than likely I guess.
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post #5 of 14 (permalink) Old 07-08-2019, 02:16 PM
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Crimped and soldered... belt and suspenders. Only one is necessary in either case.

You can get away with crimping and soldering, although there's no reason to do that, in stationary devices.

Crimping and soldering on motorcycles and other devices that move can l give you the exact result you experienced.

Crimp and solder on a pre-rubber mounted engine Sportster and you're in for a walk.

Ditto on no need for insulation at ground points.
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post #6 of 14 (permalink) Old 07-08-2019, 08:13 PM
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I crew chiefed a 914/6 in the Trans Am Series in 1980.

When we built the car we crimped every connection. We knew solder would be a disaster on a vibrating race car.

But I sure understand the temptation to beef it up
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post #7 of 14 (permalink) Old 07-08-2019, 08:17 PM
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Originally Posted by Pylot7 View Post
I crew chiefed a 914/6 in the Trans Am Series in 1980.

When we built the car we crimped every connection. We knew solder would be a disaster on a vibrating race car.

But I sure understand the temptation to beef it up
Give into your temptation and "strain relief" the connections.
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post #8 of 14 (permalink) Old 07-09-2019, 05:29 AM
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good lesson for me as it's something I never knew. thanks for posting

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post #9 of 14 (permalink) Old 07-09-2019, 11:32 AM
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As a rule, a wiring joint will only fail where you have covered it with shrink wrap, bundled it neatly and professionally, and probably buried it in a spot where it will be difficult to get back to to repair.
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post #10 of 14 (permalink) Old 07-09-2019, 01:46 PM
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I will not debate soldering or not soldering crimp joints. Otherwise this thread will exceed 6 pages easy. I do it both ways. But a factor entering in here is heat. A good solder joint has to be properly done as well. Either too much or too little heat will lead to a failure. Your standard soldering gun is fast, but it is too hot for this kind of job. If you have solder wicking up the wire, you are both too hot, and are using too much solder. If your insulation is.damaged when you are done, you got it too hot. If I do decide to solder a joint like this (and there are rare occasions I do) I use a very small iron made for solid state curcuit boards. A quality iron like this has a temperature control on it. Few people realize what a real ART it is to solder really well. It is one of those side skills that has seemed to follow me from trade to trade my whole life. (everything from curcuit boards ,radiators, to 4" copper pipe) I am not an expert, but I have been soldering over 60 years. I just don't do it enough.
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Last edited by Wire-Wheels; 07-09-2019 at 02:27 PM.
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