Morris Minor Owners Club

The cloth covering on my wiring loom has substantially rotted, but the PVC covered wiring appears to be generally in a reasonable condition. Has anyone recovered their loom, either with cloth, or alternatively expanding plastic braid or similar ? I'm thinking of doing this rather than buying a new loom as it will give me the opportunity to add extra wires for electric heated rear window, washer pump, -ve Earth conversion, etc. before recovering.

I have found that when the cloth covering the loom is past its best the copper wiring inside the PVC has usually turned black and its conductivity may not be as good as it could be. Aged copper gets very stiff and movement of the wire may lead to fractures and broken circuits. There is not much you can do to anneal the copper wiring of a loom.
Personally if the cloth covering has rotted away I would consider it time to replace the loom.
Someone on here recently was discussing building up new looms with additional circuits/feeds - using the search facility may give you the details and the loom manufacturing company.

Here's the link to Autosparks https://www.autosparks.co.uk/
So long as you specify your requirements for "additional " wiring , hazards , heated rear screen , alternator , spots , etc most loom manufacturers will incorporate these into a bespoke loom. The additional cost is well worth it and produces a neat & tidy solution.
You're only going to do it once so incorporate everything " you might need " now to future proof it.

I second Phil's assessment , if the loom cloth is past it's best , so is the wiring itself. False economy re braiding an old loom. ( You could always buy a fire extinguisher for the inevitable electrical fire , with the money saved . Make sure you catch it in time .)
Bob

Thanks Phil and Bob, I suspect you are right. From experience the ends of wiring where the connectors are fitted are often black and brittle, and although I haven't got as far as inspecting all of the ends I will probably find this to be the case. I'm curious as to why car wiring deteriorates like this, I've always assumed it is a combination of exposure to solvents and heat, exacerbated by the large surface area due to the stranded nature of the cable, and an element of electrolysis when damp?

Black wire syndrome is common in the Radio Controlled modelling community, experts say it's a chemical process that causes it and it increases resistance in the circuit. The only way to counter it is to replace the whole loom.

'Negative lead corrosion' Lost one of my models to it, the wire had turned to carbon under the insulation

I used Autosparks to recover our original 1958 braided loom in 1998 and again in 2016 - the harness was fine in 2016, just that I dis-assembled the complete car prior to a re-spray, and had added a few new circuits in the previous 18 years, so decided to get the harness recovered whilst it was out of the car. There were a couple of very slightly 'dark' wires, but stripping them back a little further gave nice clean copper. In 1998 I fitted new 'solder type' bullet connectors throughout the entire harness, both original and new, and replaced a few of them again last year.

Autosparks need a sample of the original braid so they can match it, but other than that they cover whatever you give them and the service is superb. Our harness has almost as many additional circuits as there are original, but all are covered in the original pattern braid and look excellent. The only 'give-away' is that there are now 2 harness holes in the bulkhead, the original with the original circuits, and a second one with all the additional circuits a little way to the left of the original one - it also uses the standard bulkhead grommet arrangement, so even looks 'standard' as well!

If you do strip the original harness, I would strongly recommend that you re-solder all of the joints inside the harness and cover them with new heat-shrink sleeving, as well as replace all the bullet connectors.