Webber suffered Red Bull's third alternator failure in a race this year at Austin, dropping him out of third position.
That problem prompted concerns from the team about that area of the car with championship leader Sebastian Vettel going into next weekend's title showdown in Brazil with a 'ticking time bomb' deep inside his car.
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 which has left engine partner Renault in no doubt that Red Bull must switch to the newer spec.
Renault's head of trackside operations Remi Taffin said: "It is very simple. We go for the new spec. It has passed all the tests."
Red Bull elected not to use the newer specification, which was raced by other Renault teams, because it felt safer using the older specification that had so far proved trouble-free.
When asked why that decision had been made if the newer units had passed all reliability tests, Taffin said: "Because they are human beings and at some point as humans they have some feelings.
"It was a common decision, so we put everything on the table and we decided altogether we should go that way. We had everything to fit either the old or new design.
"But the feeling was generally that there is some sense to keep on using something that we have known for years with low mileage and stuff like that, even if we had a new solution that we knew had gone through all the tests.
"Maybe it is a bit more difficult to understand, but put yourself in the situation where you have to make a decision.
"Sometimes you go into a shop and there are two different things and your head says you should buy this one but your heart says you should buy the other one."
Taffin added that the fact that Renault's other teams had successfully used the revised newer specification of alternator last weekend meant that Red Bull should have no concerns about its reliability for Brazil.
"This is the first Sunday it has been used, but now we are up to 2000km on a few items with track and dyno testing, so there is nothing we would do more on this item before we fit it on the car."
Webber pulled over after his car's alternator failed 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.
Vettel, who has won five times this season, will be champion if:
- He finishes in the top four
- He finishes 5th, 6th or 7th but Alonso does not win
- He finishes 8th or 9th and Alonso does not finish better than third
- Alonso does not finish better than fourth
Alonso, who has already won three times this season, will be champion if:
- He wins while Vettel does not finish better than fifth
- He finishes 2nd while Vettel does not finish better than eighth
- He finishes in the top three, while Vettel does not finish better than 10th
In all cases where there would be a tie at the end of the Brazilian GP, Vettel would be crowned champion due to the number of wins this season, he leads 5-3 before the final round.