So, I'm an idiot. I was changing the thermostat and didn't disconnect the battery. One thing lead to another, and now I've got a very burned up 3/8 drive socket extension and a no-crank. It seems the socket extension came into contact with the alternator main power terminal.

 

Some looking led me to learn that I've popped the big fuse on the wire that comes off battery positive to feed the starter and alternator.

It's a permanently fitted crimped-in monstrosity made by AMP. There are no useful part numbers on it.

I'm given to understand that Ford would say I now need to replace that wiring loom because it's integral to it.

Not going to happen. I've bought this car on Monday afternoon following a hit and run in the morning that destroyed my previous Focus. It's not economically viable to claim on the insurance, so I'm two and a half grand out of pocket already this week. I can't afford £100 for the wiring loom and the two day wait.

I'm an electronics engineer, and have the tooling to crimp a lug onto the end of the cable where the blown fuse was. 

I've got a selection (150a, 175a, 200a) of fuses/ fuse-holders  coming from Amazon tomorrow, as I absolutely need to drive to work on Monday.

I've smashed the old fuse open, and my guess from looking is that it's somewhere around the 150 amp mark. I've read mutterings on various bits of the internet that it was 150amp but can't find anything conclusive.

Does anyone know, absolutely categorically, what value the blown fuse / fusible link thing was? It's beige plastic, directly bolted to the battery terminal lug and seems to feed just the starter and alternator.

 

 

The Inrush Current is 150Amp.

Here is the data sheet for it: https://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Specification+Or+Standard108-15175EpdfEnglishENG_SS_108-15175_E.pdf953133-1

You can probably get a lead with the fuse from a scrap yard for £20