Romain Grosjean struggled with brake-by-wire issues on Thursday, triggering three red flags on the penultimate day of testing in Spain.
The Haas driver registered 77 laps but the day was punctuated by three different stoppages, with the first two were brake-related and leaving him in the gravel at Turns 4 and 1. Haas confirmed it was struggling with his brake-by-wire system throughout the day and will look for a solution overnight.
"We are working a lot on the brake-by-wire system, obviously not with the results we wanted to have," team boss Guenther Steiner said. "Romain went off a few times. We have a brake without wire! We are breaking the car not the wire. I think it is part of the development of the car, we need to get it fixed now for tomorrow."
"We will keep on developing it, for sure. I wouldn't say that there are concerns, this is what you do when you develop. It's Ferrari's system, but we need to develop it to our needs. We cannot use their data to develop it. It's not a hardware issue, it's just an electronic issue. If you don't push the car you will never know how it goes, and we need to find this stuff out before we go to Australia, as much as possible, and we've only got tomorrow left."
The third stop, which came at the very end of the session, was caused by an engine shutdown when Grosjean went over a kerb too hard. Steiner says the brake-by-wire issue, which is linked to the energy recovery system, is part of the fine-tuning still needed on the team's Ferrari power unit. However, he said Thursday's problems had nothing to do with Haas' turbo issues from earlier this week.
Grosjean struggled with a Lotus car with brake-by-wire issues in 2014 but is confident Haas' troubles on Thursday will not continue until the season-opening Australian Grand Prix in two weeks.
"This is a very, very complicated system," he said. "We had a problem in 2014 with Lotus. I know the car is going a bit quicker this week so we are finding more issues on that system and we need to get on top of things because that's hurting us in terms of preparation, performance and setting up the car. But we're on it.
"I think it will be solved for Melbourne. Hopefully overnight we can do a big update. We have really seen today what's the problem and for the first time we know where it comes from, so hopefully for tomorrow we have some fix. That will help us a lot."
The French driver admits the issue takes away some of the confidence a driver has when approaching a corner.
"I wasn't 100 percent confident when I got back on track and had to brake for Turn 1. I probably braked 20 metres earlier than I should, but it's part of the life. We knew we would have problems. I did not expect to spin at 300 but it happens sometimes."