Viktor Blagov, deputy head of flights to the ISS in Russia, said, "first it is necessary to make a number of checks and then the system can be turned on."
Commander Michael Foale and Flight Engineer Alexander Kaleri installed a new liquid unit of the Elektron system, which is designed to produce breathing air for the ISS. The crew was given three hours to replace this component on Thursday.
Air bubble that began to appear in the faulty liquid unit prevented the Elektron system from operating normally.
The Elektron system will be modified later to ensure that the system can be used without any problems even if air bubbles reappear.
Problems with the Elektron system began roughly a month ago. At the end of last week, Mr. Kaleri and Mr. Foale tried to repair the Elektron system. To maintain the necessary composition of the air on board the station the crew used oxygen grains, as well as oxygen brought into orbit by the Progress M1-11 spacecraft.