Audi A6 starter/generator 48V repair
AUDI A6
Background to the problem
The 48V starter-generators of Volkswagen Group cars manufactured after 2018 equipped with the Mild Hybrid (MHEV) system do not deserve the best reputation. What are just a few of the brand's recall campaigns and the perception of a "mild-hybrid disaster" in the Western automotive media? The reason is simple: the system was a novelty for the brand, the designers incorrectly calculated the necessary parameters, and the device produced too much current when working as a generator.
This led to the overheating of power transistors and the failure of the generator power board. Further troubles followed the chain: the 48 V battery was completely discharged through the disconnected generator, after which the protection was triggered. We had to repair the starter generator and unlock the battery using the Audi ODIS program.
The problem has been known for a long time, and today it is successfully treated by re-flashing the starter generator and installing, if necessary, new power boards. But is this unit always to blame? Sometimes you need to be more careful when installing it. In modern cars, there are no trifles - especially when it comes to such "nonsense" as coolant and its pump.
Repair history
We received a 2018 Audi A6 for repair, a diesel car equipped with an MHEV system. Relatively recently, the customer purchased a starter generator for it from us (the previous one had burned out), but installed it himself. At the time of contacting us, the new alternator was not working again, the 48 V battery was discharged and blocked.
Diagnostic results
In addition to the standard electronic unit errors related to the starter-generator control unit and the hybrid drive battery, a critical temperature (-50°C) was also recorded, indicating a lack of coolant. In addition, we found that the customer had not updated the firmware through ODIS after installing the new alternator, which is a gross violation of the installation rules.
This was not the only violation. Since the 48V starter-generator is water-cooled, it was necessary to properly fill the cooling system after it was connected: remove the air crust and add coolant to the level. The customer did not do this, which led to the third and most serious error during the installation of the new generator.
As our diagnostics showed, the first source of the problem was not a faulty alternator at all, but a stuck electric pump. The defective water pump did not provide coolant circulation through the system and, consequently, quality cooling of the equipment.
Work performed
We had to replace the alternator because the one we sold earlier was beyond repair - it was burnt out.
- We flashed the new generator to a new version and put it into operation correctly
- We replaced the jammed electric pump.
- Fixed a critical error on the battery so it would accept a charge.
Tips and cautions
This case illustrates how important it is when repairing modern cars to turn to professionals with experience and competence, including in highly specialized fields.
It also illustrates how important it is to take into account all details and nuances and to carefully follow the work regulations.
