Red Bull faces alternator switch by the United States Grand Prix

In the wake of the double alternator failure that Sebastian Vettel suffered at the Italian GP, Renault reverted its teams back to a 2011-specification to ensure there were no repeat problems.

However, with not enough of the old batch to last the entire season, Renault has continued work on a new version to make sure it has something ready for the final races.

Renault's head of track operations Remi Taffin told AUTOSPORT that the French car manufacturer was now happy that it has a version that should not suffer the same problems that have struck this year, and its teams would have to switch across imminently.

"The alternator has been changed and modified," he said. "We had a new version we tested in Singapore, and another one in Suzuka. We ran that one again in Korea - and will do so here in India as well.

"As well as that, we were running it on the dyno and that will become the specification that we will introduce this year when we need it. But we also have other specifications that are coming from R&D that are focused on 2013."

Taffin said that there is enough of the 2011 specification to last teams through the next two races, but that a switch over to the latest version would be needed for Austin.

"I think at the latest, and obviously it depends on the mileage we do, it should be the United States," he explained.

"Obviously it is not going to be for all teams, but we don't know for who yet."

Although Red Bull may feel reluctant to move away from the guaranteed reliability of the older version because of its championship situation, Taffin said the final decision about what the team does will be made by Renault alone.

When asked how Renault will decide when teams have to switch to the new version, Taffin said: "To be very honest it is a very difficult answer, because it is not any more just a technical issue. There are personal feelings about what should be run, and there are bad memories and things like that.

"So even if we have gone through all the validation process, when you discuss about introducing a new spec of alternator - people say, 'stop, should we not just keep with the old one'.

"The key point is where is the shift point from a 2011 unit with too much mileage on, to the new spec?

"But we will take the decision as always, because for any internals of the engine you cannot really leave that to the teams. It is not because they are not technically speaking OK to do that, but there is too much of an inside [emotional] feeling."