SAN DIEGO -- Longtime San Diego radio show personalities Jeff and Jer are off the air Friday after having abruptly left Star 94.1 amid stalled contract negotiations.

Station owner Clear Channel Communications Thursday announced the departure of Jeff Detrow and Jerry "Jer" Cesak, with immediate effect.

The pair have had a morning show on Star 94.1 for the past four years. Their local radio history began in 1988.

"Despite extensive contract negotiations, 'The Jeff and Jer Showgram' has concluded its tenure at Star 94.1," Clear Channel San Diego Market Manager Debbie Wagner said in a statement.

This morning, Jack 100.7, which is owned by Midwest Television Inc., began advertising that a "big announcement" will be made at 7:10 a.m. on Aug. 31. In an interview with Fox 5, Detrow and Cesak coyly declined to confirm whether the announcement pertained to them.

However, they said they are looking to land another radio job in San Diego in the near future.

The pair left what was then Star 100.7 in 2005 to be on Star 94.1 after Midwest Television renamed the channel Jack 100.7 and changed it to a no-disc jockey format. Since then, standup comedian Monique Marvezas was hired to do a four-hour morning show called Monique and the Man. Earlier this year, the show was altered from four hours to 30 minutes a day.

Cesak told The San Diego Union-Tribune on Thursday that negotiations with Clear Channel stalled because the media giant refused to extend a renewal offer to the five people who regularly contribute on-air to the Showgram: "Little Tommy" Sablan, Randy Hoag, Laura Cain, Delana Bennett and Emily Griffiths.

"We are a family show done by a core family," Cesak said. "We won't do a show without our family. That's unacceptable."

"A.J. in the morning," featuring A.J. Machado, will replace the Jeff and Jer Showgram beginning on Monday, Aug. 31, according to Star 94.1's Web site. Machado is moving from Channel 93.3, which is also owned by Clear Channel.

It was not immediately clear whether Machado's band of sidekicks, who make up "A.J.'s Playhouse" on Channel 93.3, would be following him.