So today I finished off replacing the starter motor - pulled the thorttle body and plenum a week or so ago, then got distracted.
Anyway, also tested my Y cable (alternator-starter-battery) which I replaced around 2018. Cable is good, but there's a short somewhere in the cable to the battery, as there's some continuity with the engine block!
Anyway, I'm OK with car electrics but not a pro, so if there's anyone smart out there let me know how to investigate further!
Starter motor is done at least.
Yanked the old starter out. 13mm bolt for the Y cable, 10mm bolt for the starter wire, and 15mm bolts hold that actual starter to the engine.
Nothing wrong with the old starter, but I'd bought a new starter on sale a few years back and lockdown #4 is a good opportunity to fit it.
Did some testing - this is with battery disconnected from the car. Continuity between ground terminal and ground bolt is perfect.
However this is the weird problem - from positive terminal, there's some continuity to ground as well! Suspect a short in the positive cable somewhere.
There's also a bit of continuity between the ground and positive terminals, which I don't think is good!
At the back of the car, I disconnected Y cable from the battery cable.
Y cable has perfect internal continuity and no continuity to engine block.
Battery cable has some continuity to engine block.
Task for tomorrow - jack up the car, and trace/test the battery cable.
