[trit21]

I notice in your signature you have a 2002 3500 Open. During this time period, Cummins was using an alarm board behind the helm. If you pull the helm forward, up behind the gauges is the alarm board. My Tiara is a 2000 3500 with Cummins 6bta 370 and has the same alarm boards. Tiara has set these up to monitor oil pressure, coolant temp and voltage. The readings are obtained from the same sensors that the gauges use, they tap off the gauge sender and that little board reads the sensor and then determines if it should sound an alarm. The problem with this system, is that over time, connections become loose and the resistance changes which can cause false alarms. 

I chased a false alarm for a long time my boat. I even disconnected those little alarm boards so they would stop going off but kept a sharp eye on the gauges. 

I then determine that I had a loose ground on the main bus bar behind the helm. It is kind of buried under the switch kind of but the main connection was loose. Once I fixed that ground, other loose connections on other grounds, power, connectors for the gauges, I haven't had the problem since, I would recommend you look at the grounds all over the boat, behind helm, engine room etc and see if that fixes the problem. 

Tiara and Cummins knew of the problem and offered to replace that board with a separate alarm circuit. New switch sensor instead of trying to 'read' what the gauges were reading, new alarm horn etc etc. They even paid to have that all replaced but they no longer do that. I called them about the alarms and the girl I spoke to at Tiara said they didn't have any more of those packets but she called Cummins and in about 4 months I received the new alarm modules , switch etc in the mail FREE. Tiara really stepped up on that one, how great was that right. 

I have yet to put that new stuff in but I do have it along with the wiring diagram but once I fixed the ground issue the false alarms went away. 

If you would like any additional information, let me know and I will do what I can to scan the diagram and whatever you need. 

The problem you are having is a know issue but as long as you continue to watch voltage, oil pressure, coolant temp and make sure they are not high, low whatever, then you will be good until you can fix the issue.