The alarm is connected to both the coolant
temperature and oil
pressure senders. These are both just switches, so the alarm should either be off or on, no in between.
Have you looked to see which warning light is on while the alarm is sounding?
Does the alarm sound loud and strong when you turn the key to on with the engine
Do the charge and oil
pressure lights come on with the key on and the engine
If you have the tachometer version of the panel, the switch that turns on the instruments light when pushed to one side, tests the coolant
indicator light when pushed in the other direction.
Could be a defective oil or temp sender. They should read either as a short or open. Oil is closed (short) no pressure, coolant is open cold.
Could also be a poor connection to or from the alarm, such that you do have an engine problem, but poor alarming.