Pastor Maldonado will debut Williams new FW35 when the team takes the covers off at the start of the second pre-season test.
Williams was the only outfit that headed to Jerez, the first of the three outings, with last year's car.
The team opted to run their FW34 while evaluating new parts and the new Pirelli compounds.
However, the team will have their 2013 car available for the second test, which takes place at Barcelona next week.
The team has confirmed that Maldonado will debut the FW35 on the morning of the 19th, just moments after Williams unveil it to the world.
The Venezuelan will hand the car over to new team-mate Valtteri Bottas for Wednesday before sharing the cockpit for the final two days.