I got the Model 3 all fixed and it’s been a few days now without it catching fire or sending any error codes so the end result:
A little digital speedo. Utter bastard of a job on a RHD car and I was plagued by an unfortunate 12v battery error upon reconnecting the battery.
The 12v battery as I found out controls a pair of contacts which engage with the high voltage battery - these are sprung open so the 12v applies a constant voltage to close the contacts - this seems to be a regulatory safety thing and the 12v has a cable going round the perimeter of the car - so if you’re in an accident and the jaws of life are used it acts as a kill switch and isolates the car. So this is why a dead 12v battery on an EV = dead car.
With the 12v removed the in car electronics all function normally as the high voltage battery supplies them and there’s another plug under the rear seat which you pull to kill those - in effect this is how you do a complete computer reset to erase error codes.
So in my case the car thinks the 12v is degraded but it’s at 12.59v, so I take it out the car, reset the entire car, same error, do this another 2 times still no different. Remove battery, test it and tester says it’s good
Fully charge it on the bench, reinstall into car, reset car, still same error.
I’m thinking I’ve fucked the ”VCFRONT” module somehow which is bad, it’s expensive and needs coding to the car which only Tesla can do.
Last attempt to fix it myself is to buy a new 12v, new Varta battery is only £75 although reading the Tesla forums if you do not pay Tesla £300 to fit the official Tesla supplied battery then your car will catch fire, your dog will die and Elon won’t make love to you. They’re a special bunch.
New Varta battery installed and the fucker is happy. It must be doing some kind of more advanced battery health test but in hindsight I think the original 12v was bad, the car was consuming about 10 miles of range just parked up overnight but this has now gone down to just a few miles per night. It must have been relying mainly on its lithium pack before.
Ended up making a few other improvements to the car, actually just refitting shit which Elon probably thought was unnecessary. Fuck you elon. You twat.
Frunk before
Frunk after
There’s a set of door seals around all the doors.
I insulated the crap out of the car, there was no insulation in the boot at all apart from a foam piece over the motor so it just amplified all the noise so I put down some dynamat type stuff then went over it with a foam type thing.
Did the same to the are under the rear sets and arches, then when I ended up pulling the area under the dash/footwells to bits I did all of that too.
New Hankook Ion Evo tyres - as fitted to the new Model 3. These are amazing in terms of ride comfort and quietness, the car feels like it’s on a different suspension. There’s no steel in the tyre wall, it’s just plastic and they claim to give 10% more range than PS4S - after 1000 miles this seems to be an accurate claim. Car is like new in terms of range again! I’d go as far as to say that most of the ride improvements in the new Model 3 are probably down to these tyres.
Did some other small things too but it was a pretty busy weekend. As for the car it’s much better overall. So much more quiet it’s incomparable to how it was before.
I shan't complain though. 
