Does anyone know where the engine shutoff module for the Sea-Fire engine space fire extinguisher might be hidden on a 426DS? Recently the alarm panel in the cockpit has been making a low volume buzz or hum whenever the engine is running. Its not loud but it is noticeable. Everything appears fine in the engine space and the bottle is reading in the green. This is somewhat intermittent and it doesn't make any difference if the panel is on normal or over ride. Anybody have any ideas? Thanks.