Key on beep doesnt always sound

[chartersj]

I have had a problem with the single beep with just turning the key to the on position. Sometimes it works other times it wont. Previous own claimed it did the same thing with him. I really want to be able to know that the alarm will sound if a problem arises while running. Any idea where i could look? There is a tan/ blue and a purple wire going to the horn under the dash, if put a volt meter from a known ground to the tan/blue, that will bring the alarm to life for a while.... Serial number is 1A074806 if that helps. The boat came new with a 502 mpi and the previous owner put in the 2007 496 ho.

 

[Bondo]

Ayuh,..... The purple wire is power to the system, the tan/ blue wire goes to the sensors, which ground the horn to make it beep,.....

 

[chartersj]

Ayuh,..... The purple wire is power to the system, the tan/ blue wire goes to the sensors, which ground the horn to make it beep,.....

Ok, starting to think I must have a bad or weak connection on the tan/blue some where. So is the key on beep a signal from the computer?