I haven't looked at the float switch yet, good callThe alarm usually ties into oil pressure, engine temp or drive fluid levels. If the buzzer stays on after startup, check the oil pressure switch and temp sensor wiring for grounding issues. Some setups also trigger alarms from low drive oil via a float switch. Have you checked fluid levels and confirmed the sensors aren't stuck or shorted?
When you say disconnect the alarm wire, is that safe to do while the engine is running, or should it be completely off first?I feel you should check the usual suspects first, that is low oil level, overheat sensor, or faulty buzzer wiring, or even a bad sensor will trigger the alarm even if everything's fine. Try disconnecting the alarm wire at the motor and see if it stops, just to help narrow it down.