ACE 04 has experienced mechanical problems and is 20 minutes behind schedule after departing the Fremont station. The generator for the head-end power unit is not functioning properly and the train is operating on battery power. Because of this, the train must slow to 20 mph at each signal crossing for security and safety purposes. At this time, I anticipate ACE 04 arriving into the Stockton station approximately 30 - 40 minutes behind schedule.