1999 merc alarms not working but get a start beep

[Cady8special]

Just got a 1999 merc 135. When I turn the key I run I get a beeeep beep beep. I figure that means the system is good. But I pulled the oil cap (with float) while running and he alarm did not sound. I checked and I have resistance with the float down and an incomplete circuit when up- the way it should be. I pulled the alarm module ground- when I take it off ground then re-ground it out in the run position it gives a steady beep. Any ideas as I what might be wrong here? Thanks guys.