Scrippy wrote This is not just a coincidence. Think what you want but it was a direct result of the power cable work. Other folks are having issues with CIC headunits dying after as well. I would assume a few things....
1-The tech is cutting the line with battery still connected and splicing in new wiring to be efficient with time as opposed to execution.
2-The tech is suffering from Parkinson's disease so the reconnection of IBS to battery is chattering before a solid connection is made.
In any case I could care less how they are dropping the ball. Let me be clear that my car is serviced like a proper OCD would so this and my 3 friend failures are not just coincidences. Also another bizarre fact is that the power cable is not being done the same way across vehicles after the work was inspected on my car and the other 3. My vehicle has no splice but whole new positive cable. The point of splice on my friends cars are done at different points. All of this makes me feel like you will be hearing more of these posts as more people have work done. Anyone wanna bet $20?
Can't comment about the workmanship of your dealer but I can provide alot of detail on the power cable.
My first 2011 E90 M3 had the intermittent power issue and the car actually stranding me several times even thought battery and alternator had no issues. Got so bad it was towed to the dealership and by luck did not have power when they got it. BMW at the time said the recall for other 3 series did not apply to the M3 which did not make sense. Lucky the car was under full warranty still so they had to cover it.
The issue is that corrosion builds in the cable and actually works its way down the cable. The initial recall for 3 series was to replace the entire cable. I assume this was a very expensive repair as the battery is in the trunk.
The revised procedure was to cut the cable closer to the fuse box but I believe they did this to make the procedure quicker and cheaper. They cut in different spots as the corrosion works it way down the cable so assume the longer the issue is, the further the cut they make.
On my next 2011 E90 M3 they cut the cable short and did not replace the whole cable.
In terms of repair, the instructions states to disconnect the power. Not sure even if I was trying to short cut the repair that you would attempt to cut the cable without removing power first. The cable is thick, the crimp to connect the new one is large. It would open the installer to alot of risk of electrocuting oneself compared to the simple job of disconnecting the power which is very easy on the e90 compared to the previous generations.
What I suspect with some of these poor repairs is the crimping of the new cable. If I had a choice, I would prefer an entire new cable, less risk of connection issues as you don't need to rely on a crimp connection which I believe can be poorly done but then you risk poor reinstallation of the interior parts that are removed to install the new cable.
