Technical Soldering automotive wiring

X-cpe · Mar 29, 2025 at 6:14 PM

Harv said: ↑

The Thomas and Betts crimpers are awesome. Crazy Steve recommended them in his wiring-101 thread, and I imported a pair from the US. He is right - they make a repeatable crimp that will not fail. Took me from a "most of my crimps work" to a "confident in what I do" person. Thanks again Steve.

I suspect Jim is right - soldering or crimping can work, provided the person doing it has skill and patience.

A question for those who solder old wiring harnesses please. Most of the stuff I play with is GM Holden factory wiring that dates to the 50's and 60's. It's PVC coated, multiple strand wiring. The wiring is generally in good shape, insulation color still bright, not oily, insulation flexible. I can strip the insulation easily enough. The copper is rarely bright after the insulation is removed. I understand the basics of soldering - clean wires, heat wires not coil of solder, solder should wick in, allow to cool, joint should have mechanical strength. I can solder two new wires together without many dramas. I still struggle on a lot of the old harness soldering. The wires do not seem to want to wick up the solder.

I've tried:
a) tinning each of the two wires first the joining the tinned wires (often can't get the wires to tin).
b) using resin core and non-resin core solder. The solders are for wiring, and come in coils.
c) heating the wire a little more (to the point the insulation starts softening).
d) heating the wire a little less.
e) cleaning the wire strands with abrasive paper until they are bright copper.
f) cleaning with abrasive paper then thinners.
g) spreading the wire strands slightly.
h) twisting the strands to tighten them slightly.
i) cutting the wire further and further back to find "a good piece".
j) making sure the soldering iron is clean before starting.
k) changing soldering irons (a poor tradesman blames his tools).
l) changing solder suppliers.

I still struggle to get the old wires to wick... this then made me a "can't solder for sh$%, better learn to crimp properly" person. Appreciate views on what I am doing wrong with the soldering please.

Cheers,
Harv
Click to expand...

I think your problem lies in the fact it is almost impossible to get the total surface of every strand sufficiently mechanically and chemically clean.

1971BB427 · Mar 30, 2025 at 11:25 AM

woodiewagon46 said: ↑

chicken, one of the guy's in our club had a '40 Ford with an intermittent problem where he would loose his headlights every so often. Every time he put a meter on the terminal strip it showed he had voltage to the lights. He climbed under the dash asked a fellow club member to yell if the lights went off. He started tugging on each individual wire and the feed to the headlight pulled right out and the shrink sleeve was the only thing holding the wire in the wire end.
Click to expand...

That's not the fault of the heat shrink! It's a bad joint or crimp, or solder. It wouldn't matter what was covering that connection if it was done poorly, so no reason to blame the heat shrink. Heat shrink wont cause a bad connection to be worse.

Crazy Steve · Mar 30, 2025 at 12:09 PM

Montana1 said: ↑

I found this to be helpful and simple...

Click to expand...

Not one of the shown crimps is right... Typical 'net misinformation. I will give credit for showing a correct non-insulated crimp in the video.

Boneyard51 · Mar 30, 2025 at 12:20 PM

Harv said: ↑

The Thomas and Betts crimpers are awesome. Crazy Steve recommended them in his wiring-101 thread, and I imported a pair from the US. He is right - they make a repeatable crimp that will not fail. Took me from a "most of my crimps work" to a "confident in what I do" person. Thanks again Steve.

I suspect Jim is right - soldering or crimping can work, provided the person doing it has skill and patience.

A question for those who solder old wiring harnesses please. Most of the stuff I play with is GM Holden factory wiring that dates to the 50's and 60's. It's PVC coated, multiple strand wiring. The wiring is generally in good shape, insulation color still bright, not oily, insulation flexible. I can strip the insulation easily enough. The copper is rarely bright after the insulation is removed. I understand the basics of soldering - clean wires, heat wires not coil of solder, solder should wick in, allow to cool, joint should have mechanical strength. I can solder two new wires together without many dramas. I still struggle on a lot of the old harness soldering. The wires do not seem to want to wick up the solder.

I've tried:
a) tinning each of the two wires first the joining the tinned wires (often can't get the wires to tin).
b) using resin core and non-resin core solder. The solders are for wiring, and come in coils.
c) heating the wire a little more (to the point the insulation starts softening).
d) heating the wire a little less.
e) cleaning the wire strands with abrasive paper until they are bright copper.
f) cleaning with abrasive paper then thinners.
g) spreading the wire strands slightly.
h) twisting the strands to tighten them slightly.
i) cutting the wire further and further back to find "a good piece".
j) making sure the soldering iron is clean before starting.
k) changing soldering irons (a poor tradesman blames his tools).
l) changing solder suppliers.

I still struggle to get the old wires to wick... this then made me a "can't solder for sh$%, better learn to crimp properly" person. Appreciate views on what I am doing wrong with the soldering please.

Cheers,
Harv
Click to expand...

You are doing nothing wrong. Old dirty wires are hard to solder. I run into this a lot on old trailers. I clean them the best I can, then heat and apply the solder and keep applying solder and let it drop off, it will usually bond .

Bones

firstinsteele · Mar 30, 2025 at 1:14 PM

Crazy Steve said: ↑

Not one of the shown crimps is right... Typical 'net misinformation. I will give credit for showing a correct non-insulated crimp in the video.
Click to expand...

Agree! Guilty in the past. No more.

Ben

Corn Fed · Mar 30, 2025 at 1:30 PM

Crazy Steve said: ↑

Not one of the shown crimps is right... Typical 'net misinformation. I will give credit for showing a correct non-insulated crimp in the video.
Click to expand...

Haha I love it. One guy's right is another guy's wrong.
Just another reason I solder my joints... because my crimps would be wrong to someone no matter how they were done.

Sharpone · Mar 30, 2025 at 1:54 PM

Crazy Steve said: ↑

Not one of the shown crimps is right... Typical 'net misinformation. I will give credit for showing a correct non-insulated crimp in the video.
Click to expand...

Thanks for the insight Steve
Dan

Harv · Mar 30, 2025 at 3:13 PM

X-cpe said: ↑

I think your problem lies in the fact it is almost impossible to get the total surface of every strand sufficiently mechanically and chemically clean.
Click to expand...

Boneyard51 said: ↑

You are doing nothing wrong. Old dirty wires are hard to solder. I run into this a lot on old trailers. I clean them the best I can, then heat and apply the solder and keep applying solder and let it drop off, it will usually bond .
Click to expand...

Thanks gents - appreciated.

Cheers,
Harv

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Technical Soldering automotive wiring

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