Sebastian Vettel had criticized Magneti Marelli after Monza, now it's Dieter Mateschitz who took the unprecedented step as an engine customer of demanding Renault change component suppliers in an interview in Autobild.
This all stems from the alternator failures in Valencia and Monza. Renault engineers thought they had the problems solved after the European GP when overheating was suspected, rotors were redesigned and power consumption in the engine reduced on startup.
|a Magneti Marelli alternator|
Remault design and spec the alternator which is then built by Magneti Marelli. Marelli is not exactly a fly by night operation and they built a few alternators in their last 80 years in motorsport. Renault's alternator is not some radical new design and Magneti Marelli alternators are running fine in Ferrari engines, albeit in water cooled form.
What's going on here? Marelli being a FIAT group company it's tempting to go the conspiracy route, it's certainly a lot easier than admitting to a design issue somewhere. Overheating, vibrations from hitting the limiter regularly, all theories I've read but Red Bull are putting the blame squarely on Renault, the is no problem with the chassis according to Helmut Marko. What's certain is that Renault will bring a number of different units, older ones, and new ones reinforced where weakness was found and will decide after Friday what to use in the race.
Reliability and consistency has, of course been key to this championship so you can see what Mr. Red Bull is a bit peeved.