Electrical and technology upgrade issues have pushed back this month’s planned opening of the Warm Springs/South Fremont BART Station to early fall.

Paul Medved, project manager of the Warm Springs extension, said one cause for the latest delay stems from the need to extensively test the connection between the state-of-the-art technology and communications system of the new station and that of the 45-year-old Fremont BART Station.

A second cause is the traction cables that are supposed to energize 5.4 miles of new tracks. They are too old to power test trains running between the two stations and have to be replaced, he said.

Although the new station on Warm Springs Boulevard near South Grimmer Boulevard has seen its opening dates postponed from late 2015 to this summer and now to late fall, Medved said the project still is expected to hit budget at $767 million. An additional $54 million will be spent to buy 18 new trains BART plans to add to its fleet in the next year.

Testing of several systems such as communications, train control and power traction are expected to continue through next month, he said, and the new station should open four to six weeks after that for the 6,000 to 7,000 daily riders expected to use it.

“Every day that passes brings us to certainty that this fall is the right time frame,” he said. “The cable replacement is on schedule and should be in place by early September and we can continue to keep testing through the current cable so we don’t get delayed. … We wouldn’t want to depend on an unreliable power supply. We can limp through on testing, but we would not feel comfortable on risking starts and stops until the new power has arrived.”

On another front, Medved said BART is working with the Santa Clara Valley Transportation Authority, which has been overseeing construction of the 10-mile Berryessa extension that will bring new BART stations to Milpitas and Berryessa by fall of next year.

Because VTA handles all public transit in the South Bay and because Santa Clara County didn’t join Alameda, Contra Costa and San Francisco counties in forming the Bay Area Rapid Transit system decades ago, VTA will build the Milpitas and Berryessa stations and let BART operate them, VTA spokeswoman Brandi Childress said.

She added VTA took over construction from where the BART Warm Springs/South Fremont Station ends. That entailed building two miles of tracks in Fremont, 4.5 miles in Milpitas and 3.5 miles in San Jose for the 10-mile extension.

The Milpitas and Berryessa stations are expected to see an estimated 23,000 daily passengers on opening day — about 13,000 at Berryessa and 10,000 at Milpitas, Childress said, adding those numbers could double by 2030.

The Warm Springs station will feature an at-grade island platform with an overhead concourse and connections to VTA and AC Transit buses, in addition to taxi and passenger drop-off areas.

There will also be 2,000 parking spaces and access for pedestrians and bicyclists.

Medved said BART is “very grateful to the people of Fremont for their patience. We know how long they have been waiting to access Warm Springs. We are just grateful for their patience as we get to the finish line and get through testing and get the new power cables ready to go in the fall.”

Contact Aliyah Mohammed at amohammed@bayareanewsgroup.com or 408-262-2454 or follow her on twitter.com/Aliyah_JM.