If it is becoming a common fault with our vintage A2s, maybe the topic deserves a 'sticky' somewhere, under Maintenance perhaps. I would also re-iterate the point made elsewhere on this forum that it is impossible to tell from just a visual inspection of the earth point whether it's in good condition. Mine looked great on the outside, not a spot of corrosion on it. It was only when the bolt was out that I could see the layer of grey oxidey stuff on the surfaces. Might also be a good idea to seal the repaired connection with something water-repellent e.g. copper grease.
It's been a couple of weeks since I fixed this starter motor earth problem, and quite aside from rectifying the actual problem of not starting, I noticed other improvements
- it runs so much better, engine sounds better, there is more power under acceleration and cruising in 5th. I guess the deterioration happened more or less gradually and therefore wasn't so obvious, but the step improvement is very clear
- intermittent central locking failures have not recurred since, normally I was seeing these at least once a week and more often in cold and wet weather like we have now
- idling speed is back down from 1000rpm to what it used to be at ~800rpm
I am hoping other gremlins won't be coming back also
- spurious ABS, power steering dash lights, maybe too early to say after just two weeks but so far so good
- climate control unit locking up in MAX airflow after a failed first start when immediately followed with another (successful) start
- step changes in headlight brightness, nothing major just enough to be noticeable
I suspected already that a bad starter earth may indirectly affect the car's electronics. Couldn't reconstruct enough of the schematic from the current flow diagrams for the A2 in ELSAWIN but it's clear that the starter motor earth is shared with the alternator and affects battery charging, quite possibly more besides. According to this:
https://axleaddict.com/auto-repair/Bad-Engine-Ground-Symptoms-and-Diagnosis
Symptoms of a bad engine ground may include:
- Dim lights
- Flickering lights
- Electrical devices working erratically
- Faulty fuel pump
- Slipping or burned out AC compressor clutch
- Intermittent failure of sensors
- Damaged throttle or transmission cables
- Hard starting
- No-starting
- Dead battery
- Introduce radio noise
- Ignition coil failure
More worryingly:
Even more, bad engine grounds can also cause damage. If too much current tries to find proper ground unsuccessfully, it will choose an easy path through transmission components, transmission cable, throttle cable, wheel bearings and narrow ground wires, causing severe damage to these and other components.
I had noticed also that gear change would intermittently become difficult, then just as suddenly it would be back to normal. I am hoping no lasting damage was done..