Renault has admitted that it still has not got to the bottom of its alternator problems, in the wake of the recent failures that hit Sebastian Vettel.
Ahead of tests of a new design that will be completed by Vettel and team-mate Mark Webber in Friday practice at Singapore, Renault says it does not fully understand why it suffered three failures in Monza.
Analysis of the two broken Red Bull alternators from Monza - plus the one used by Jerome d'Ambrosio that was about to break - have narrowed down the issue to specific internal components, but the French car maker does not yet know why those parts are failing.
That is why it wants all its cars to race in Singapore with an old batch of alternators, which had been used without problems after Valencia before an updated design was brought in at Spa.
Red Bull will also use the old specification from Saturday, after testing the new design on Friday.
Renault's head of F1 track operations Remi Taffin said that his company was not yet able to say it was sure about the reasons for the failures - which makes it hard to implement a solution.
When asked if there were still question marks, he said: "Definitely. We are engineers and we have to stay honest with what we are doing. Until we have proof that it is okay to do a race, or two, or three then we cannot be satisfied.
"We hope we will be able to do more than one race with an alternator soon, but I will never say it is 100 per cent. But be sure that we are working on it and it will be fixed soon."
Taffin says that Renault has made progress in understanding what part of the alternator is failing, but it now needs to work out why it is happening.
"We had a bit of fortune by having an alternator that nearly failed on the Lotus car on Saturday [at Monza], so we could strip that down and obviously everything was not melted because this alternator was okay to run.
"We could look at the internals and we could see that some of the internals were not right. So we had a clue of what is failing. It does not mean we know why it is failing, but at least we know what part is the first to fail and this has now given us a new direction to look at.
"Obviously we need to stay honest and we are not going to have 100% a solution tomorrow.
"We have more than one solution now to apply, and we have brought one here. We are going to run it on Friday on both cars on the Red Bull to try and get some knowledge because we have a validation process we need to go through, so you cannot do shortcut. "
Taffin said that the plans to revert Red Bull back to the old design of alternator would only be changed if Renault's other teams suffered any problems in Friday practice with the old batch.
If the tests of the new design are successful, Taffin suggested that it could be ready to race as early as the Japanese GP.