Corrosion in wire.

[Dave Plowman (News)]

I'm in the process of fitting a different ECU to the old car and bought a NOS engine loom to modify. Basically just change the ECU multiplug and add a couple of sensors. The loom came in a sealed plastic bag with the original Rover sticker on it. And appeared to be as it left the factory - still nice and flexible. But on hacking off the Lucas multiplug to replace with the required D37 connector, I was surprised to find some of the conductors lightly corroded. Only a few, though - most were bright copper. I've seen this on old car wiring where it's been exposed to damp etc, but this appeared to have been well stored, even although more than 20 years old.

Any tips for removing the corrosion as it has to be soldered rather than crimped as the original plug was. Short of just scraping it off?

[Jules]

Hack it off if there's enough slack. I've had success with just scraping before - but I suspect it's nowhere near as mechanically strong as a 'proper' joint, even if it ends up electrically OK, and might just be asking for trouble 20 years down the line.

[Donwill]

Rub them between two pieces of very fine emery paper.

Don

[Dave Plowman (News)]

Sadly, there's not. And experience with this sort of corrosion says it usually goes quite a way in. But after cleaning the end and making the correction the circuit shows a decent low resistance on my ESR meter. But most of the sensors have a fairly high resistance anyway - so a few ohms probably wouldn't matter unless it got worse. The injector drive circuits are fine - and they do need to be low impedance.

I'll be dead by then. ;-)

I usually just scrape with the edge of a blade. I was hoping someone had a chemical solution. That didn't cause problems later on - like an aggressive flux can if not completely removed afterwards.

[Jules]

Yes, I usually find that, too. If it's one or two wires I'll usually cut the damage out and then solder/heatshrink some short runs of replacement wire in - I'd built up quite a collection of different wire/stripe colour combinations in the junk box before I moved overseas :)

Pain in the butt doing it for big multi-way runs, though.

Sure, leave your mess for someone else to sort out ;-)

I'd be interested to know if there is one, too. I suppose in principle it's no different to removing corrosion from any other metal, with the bonus that it shouldn't matter if there's pitting left behind as it's not a cosmetic thing.

Problem is, I assume that the corrosion weakens the wire as well as making it harder to solder to - so if it goes in a few inches it's just asking for failure at some point - and any chemical treatment probably won't reach under the insulation...

cheers

Jules

[Peter Parry]

I've used fibreglass pencils with success

stroke along the exposed wires. Easier than glasspaper and less damaging than a knife.

(free delivery today for all CPC orders)

[Dave Plowman (News)]

They make me itch...

But not the handling charge on small orders.

[Peter Parry]

No handling charge today (although it shows). Removed after order as it says on the little box to the right.

[fred]

In article , Dave Plowman (News) writes

They say that all delivery and handling charges are waived today as long as the code provided on the front page is entered in the 'Special Instructions' box at checkout.

Problem is that there is no Special Instructions box at checkout, only Order Comments and Delivery Instructions. From speaking to them, Delivery Instructions is where to put the code.

Unfortunately, the discount will only be applied when the card is debited meaning that your order confirmation email will still show the handling charge.

An awkward and uncertain process to say the least but I have a call logged to confirm that my order meets their criteria.

Thanks Peter.

[Dave Plowman (News)]

Bugger. Think I may have cocked things up.

[Ian White]

Thanks, Peter. I had the same problem and also the same fibreglass scratch brush - just never put the two together. Stranded copper that had been black with corrosion came clean enough for either soldering or crimping.

For other applications, CPC also have brass bristle refills... but has anyone seen the same in stainless steel recently? They seem to have disappeared from the market.

[fred]

In article , Dave Plowman (News) writes

Give them a call and they may take pity on you, it's not a particularly clear procedure. Ah, just noticed the lines close at 7pm so it will need to be tomorrow.

[Jan Wysocki]

I've come across this many times with old wiring looms. The copper oxide film appears to form all along the wires, under the sheath. I dip the exposed copper in warm dilute acid: usually citric - sulphuric or hydrochloric would be quicker. (IIRC sulphamic acid doesn't work.) Stop when the copper is errm, copper cloured. Rinse it well afterwards with boiling water. Scraping is ok for single core, but not good enough for soldering multicore. I guess that a fibreglass brush could work on multicore.

[Dave Plowman (News)]

Thanks - I'll give that a try when I next come across it.