(CNN) -- The final launch of space shuttle Endeavour is now scheduled for May 16 after a delay caused by an electrical fault, NASA said Monday.

The next launch attempt will be at 8:56 a.m. EDT, said NASA Space Shuttle Program Launch Integration Manager Mike Moses.

NASA had previously said that the final flight for Endeavour would be no earlier than May 16. Before that, it had said the launch wouldn't be before May 10.

A short in the heater circuit associated with the orbiter's hydraulic system caused the cancellation of Endeavour's April 29 launch, officials said. Technicians worked over the weekend to repair and retest the electrical system.

NASA repair crews replaced a faulty switch box last week and installed and tested new wiring. The heater system is working properly now, they said.

The flight is the last planned mission for Endeavour as NASA retires its shuttle fleet. The orbiter entered service in 1992 as a replacement for the ill-fated Challenger.

The scrubbed April 29 launch postponed what promised to be an emotional moment for the shuttle's commander, Mark Kelly.

Kelly's wife, U.S. Rep. Gabrielle Giffords, D-Arizona, traveled to Florida hoping to watch the shuttle's ascent. Giffords was shot in the head during a January 8 assassination attempt at a public event in Tucson, Arizona, and has been recovering at a Houston rehabilitation hospital.

Giffords later returned to the TIRR Memorial Hermann center in Houston, according to a post on her Facebook page. She is expected to attend the next launch attempt.

CNN's Rich Phillips and John Couwels contributed to this report.