Red Bull wary of faulty alternator
Technical head Newey hopes ‘ticking time bomb’ does not act up
Vettel leads Ferrari's Fernando Alonso by 13 points ahead of the final round at Interlagos after finishing runner-up to McLaren's Lewis Hamilton in Sunday's US Grand Prix in Austin, Texas.
While Red Bull clinched their third constructors' title in a row, the celebrations were muted by Vettel being denied his third successive crown for at least another week and reliability problems affecting Australian team mate Mark Webber.
"Reliability is a concern, it's unfortunately our third alternator failure this year which is a ticking time bomb," Red Bull's technical head Adrian Newey told Britain's Sky television.
"You never know when that one is going to strike. Renault haven't managed to find a proper solution to that one so that's a continual worry in the back of our minds as is the rest of the reliability.
"The cars are very complicated and keeping them going around is anything but guaranteed."
Webber pulled over after his car's alternator failed, a recurring problem for the Renault-powered team this season, while he was running in third place at the Circuit of the Americas.
A similar failure halted Vettel at the European Grand Prix in Valencia while he was leading and the 25-year-old German also suffered alternator problems at Monza in Italy when he stopped six laps from the end.
Other Renault-powered teams have had reliability problems and the manufacturer made new specification alternators available for the race in Austin.
With so much at stake, Red Bull stuck with the type they had used since Monza without trouble only for Webber to pay the price. "We had low battery voltage for a few laps before and then I lost gearbox sync and KERS, something was happening on the battery side," said the Australian.
Team principal Christian Horner hoped they would have the new version for Brazil and Vettel was confident his team would resolve the issue.