40 year old wiring !!!

[Nurse Julie]

Had a problem with Millie, the CB550 mongrel that Trig has built for me. The bike has got a brand new CB500 single fuse loom fitted but we used the original battery earth cable as it looked in good nick. Whilst doing the electrics on the bike, everything electric worked, including the engine firing. The other day, when Trig pushed the start button, all the idiot lights went out, no firing and after a short while the idiot lights came back on again. Now, as many of you know, wiring is Trigs least favourite subject, so he consulted with Mr Hairy who said it could be a bad earth, all checked, all ok. The only thing Trig could find was the earth to the battery seemed a bit lumpy inside the outer cable. After cutting the outer sleeve off, this is what he found....totally disintegrated copper wire. He made a new earth cable and hey presto, all tickity boo and everything working as it should do. Thanks Hairy, I have emailed you the pics.


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[UK Pete]

Oh wow all hidden away ..just shows how bloody annoying fault finding can be

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[paul G]

They don't call it electrickery for nothing

[hairygit]

That's why I always suggest using a car jumplead to bypass the earth cable, poor earthing is the root cause of a lot of faults. Vibration over 40+ years has caused fatigue in the cable strands, plus water ingress has corroded them as well.

[Orcade-Ian]

Wait till you start fault finding on one of these CANBUS equipped modern cars!  The wires are like the stuff spiders make webs from and the insulation is only as thick as my hair (used to be).

I’ve just repaired the loom on the bootlid of my Daimler which is only 18 years old - the wires just snapped off.

Ian

[mike the bike]

It only takes a nick in the insulation for the salt water to get between the strands and corrosion will set in.  It can be right tricky to find.

[Woodside]

age doesnt affect the copper like that or indeed the water.......a poor/loose connection make that happen ...and when you add a large load (amps) like a starter motor that is over used on a poorly engine ...thats what makes the cables over heat and the copper (nigel will explain) completley flake out..
i expect the insulation was like rock too

[Nurse Julie]

Surprisingly Jason the insulation wasn't too bad. I understand what your saying about the load. I think Trig using it whilst testing all the other electrics and firing the engine just about finished it off. Never mind, nice new cable now and a lovely engine so shouldn't give any further trouble.

[Woodside]

 the load on these cables can be extreme especially on the 12v system....the lower the voltage the more the amps ramp up...add a loose connection ...and it can fry a loom in seconds...
if the copper is black its been fried..
it tends to go green with age and general weathering ..look at church roofs.
either way thats an arse to find an you would never expect the largest cable on the system to be compromised....
i never commented on the other thread but that bikes a beauty...shows you dont need to chop the buggery out of a bike to make it cool....

[Nurse Julie]

i never commented on the other thread but that bikes a beauty...shows you dont need to chop the buggery out of a bike to make it cool....

Thanks Jason. It's a bike befitting a woman of my age I think, a bit different but totally rideable without having my boobs on the tank and my legs at ridiculous angles on rearsets !!!.

[Woodside]

not like this i hope

[Nurse Julie]

Haha, I have seen that pic before, did you send it to Trig?.

[K2-K6]

Looks fried to me too,  and along time before you've worked on it recently judging by the green corrosion as Jason pointed to.

Haven't seen that on a bike that I can remember as it's quite a reasonable size.  I put redundancy in by adding separate cable on rally cars incase you loose one, if you crank a car with an iffy earth it'll try and track back from the engine via the throttle cable as it'll find circuit through there and melt it because it can't support the load.

I guess it's looked at that the positive is supplying the power so the earth is not at first suspected but the load is all the same right round back to the battery.