New Andover wire harness

Peter Restaino · 2026-02-08T20:36:02-0700

Was testing a new harness and found one rear brake switch wire was open circuit and it took a while to find the male spade connector crimped over the insulation and the other thing is why they dont solder all the connections. The only ones solderd are the grounds. Rant over.

Fast Eddie · 2026-02-09T00:17:50-0700

In trains, planes and automobiles soldering is generally avoided as it makes the wires brittle.

kommando · 2026-02-09T01:24:25-0700

As FE says its standard practise to rely solely on crimping where vibration levels are high.

robs ss · 2026-02-09T02:57:59-0700

My understanding is that it is not the soldering that causes brittleness but rather the very localised bending and subsequent work hardening of the copper immediately beside the soldered joint.
Copper will work harden until it is as brittle as glass.

If you want to stop the "green death" of crimped joints then either use "tinned" wire or dab some ACF-50 (or similar) on the joint.

Fast Eddie · 2026-02-09T03:08:04-0700

robs ss said:
My understanding is that it is not the soldering that causes brittleness but rather the very localised bending and subsequent work hardening of the copper immediately beside the soldered joint.
Copper will work harden until it is as brittle as glass.

If you want to stop the "green death" of crimped joints then either use "tinned" wire or dab some ACF-50 (or similar) on the joint.

You would also get the same ‘localised bending’ immediately after a crimped connector tho, so I think the heat must be effecting things somehow?

kommando · 2026-02-09T03:16:52-0700

Its the sharp transition from a wire with solder to without solder where the solder has wicked into an unsupported wire ie outside the crimped zone. There can be 2 crimps. If you could guarantee the solder only stayed in the first crimp directly onto the wires then it would be fine, but you cannot guarantee that in a production environment to even not migrate past the 2nd crimp onto the still covered wire. Where there is only one crimp ie bullet connectors it even less controllable.

Andy Higham · 2026-02-09T03:17:59-0700

Getting someone to sit with a soldering iron and solder every connector would probably add £25 to the price

robs ss · 2026-02-09T03:29:04-0700

Fast Eddie said:
You would also get the same ‘localised bending’ immediately after a crimped connector tho, so I think the heat must be effecting things somehow?

No
The heating process anneals copper.
I used to think you had to cool copper slowly to properly anneal ( like steel).
Not so. Since copper has no carbon in it (unlike steel) there is no carbon to be trapped at grain boundaries (causing steel's hardness) - so rate of cooling of copper does not matter to the annealed product.
@kommando described the process well (above)

concours · 2026-02-09T03:43:59-0700

Peter Restaino said:
Was testing a new harness and found one rear brake switch wire was open circuit and it took a while to find the male spade connector crimped over the insulation and the other thing is why they dont solder all the connections. The only ones solderd are the grounds. Rant over.

There are two Takeaway items here. Number one New doesn't always mean better.
Number two if you wanted it, soldered connectors, you could've made it yourself.

robs ss · 2026-02-09T03:56:00-0700

If someone offered me a new soldered harness for nothing I would say "no thanks" - I don't need the grief.

Fast Eddie · 2026-02-09T04:52:33-0700

robs ss said:
No
The heating process anneals copper.
I used to think you had to cool copper slowly to properly anneal ( like steel).
Not so. Since copper has no carbon in it (unlike steel) there is no carbon to be trapped at grain boundaries (causing steel's hardness) - so rate of cooling of copper does not matter to the annealed product.
@kommando described the process well (above)

Got it.

What I can envisage now is that the annealing may be an issue. You have a solid soldered blob, a short piece of freshly annealed copper, and then back to the ‘standard’ harder copper. Whatever the accurate root cause is, I believe it’s the dynamics at play here that causes issues.

MexicoMike · 2026-02-09T04:54:15-0700

FWIW, years ago a car I owned had ONE (factory) soldered connection for the wiring harness in the engine compartment. It was a wire with no inherent flexing of components but it broke/was re-soldered several times at the solder/wire interface. It broke simply due to V8 engine vibration.

concours · 2026-02-09T05:18:10-0700

MexicoMike said:
FWIW, years ago a car I owned had ONE (factory) soldered connection for the wiring harness in the engine compartment. It was a wire with no inherent flexing of components but it broke/was re-soldered several times at the solder/wire interface. It broke simply due to V8 engine vibration.

Mike, what component was it? What wire? What car? What engine? Just curious… I'd like to know these things. Even though I likely won't have a car exactly like you had, similarities exist all throughout the industries.

MexicoMike · 2026-02-09T05:36:13-0700

It was a 1968 Plymouth 340S fastback Barracuda. The wire was the only soldered wire in the harness and was connected to the water temp sensor. Why they used a water temp sensor that required a soldered connection rather than a spade or screw terminal, I have no idea. OTOH, except for the necessary resoldering occasionally, that sensor worked fine for the 120K+ miles I put on the car.!!

concours · 2026-02-09T05:43:28-0700

MexicoMike said:
It was a 1968 Plymouth 340S fastback Barracuda. The wire was the only soldered wire in the harness and was connected to the water temp sensor. Why they used a water temp sensor that required a soldered connection rather than a spade or screw terminal, I have no idea. OTOH, except for the necessary resoldering occasionally, that sensor worked fine for the 120K+ miles I put on the car.!!

Was that the sensor with a brass "button" shaped connecter? The almost-a-spade connector slides on from the side?

MexicoMike · 2026-02-09T05:54:29-0700

There was no connector per se - the wire was soldered directly to a brass tip with a depression in it to accept the wire/solder. However, I bought the car used so it's POSSIBLE the sensor was not the original OR that originally there was some sort of connector - seems unlikely but possible. But whether original or not, it demonstrated that solder/vibration didn't go well together.

kommando · 2026-02-09T06:00:01-0700

You can strengthen the transition point by shrink wrapping a length of plastic rod/ cable tie over the top, this will significantly reduce the bending.

JimNH · 2026-02-09T06:41:14-0700

A&P (aircraft) mechanic here and I can agree that soldered wire connections are frowned upon. A crimped connection is nice flexible wire right up to the terminal whereas solder will make for s stiff connection that's ready to fatigue off. It's hard not to have some wicking up the wire. Soldered connections are not forbidden and are used in some applications such as mic and phone jacks but the caveat being the wires have to be otherwise supported - not just dependent upon the terminal connection. Almost everything is a crimp type connector. Older planes may have hundreds of soldered pins in a connector but the back shell supports the wires so there's little chance of breaking. Most everything nowadays is crimped as it's faster and generally better all around. A fatigue break inside the insulation can drive you nuts chasing an intermittent.

Peter Restaino · 2026-02-09T09:48:38-0700

Ok good info. I solder repaired the spade connector and a couple of other kinda slightly loose bullet connectors but I ACF 50 all the rest . Thanks for the feedback.

seattle##gs · 2026-02-09T09:59:13-0700

kommando said:
As FE says its standard practise to rely solely on crimping where vibration levels are high.

I always use a bit of shrink tube at each joint for strain relief. You could solder each joint AND use shrink tube but that would take forever and a day.

New Andover wire harness

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