Found this on another forum. Hope I'm not violating anything by posting it here
(VRO Horn Warnings)
1 - A steady constant beep = Overheating - The V/6 engines, possibly some others, have a fuel restriction warning which is also a steady constant beep.
2 - A beep every 20 or 40 seconds = oil level has dropped to 1/4 tank. (Late model engine = Every 40 seconds)
3 - A beep every other second = VRO failure, air leak in oil line, oil restriction, (anything that would result in a lack of oil being supplied to the engine).
NOTE - If the warning horn is the black plastic (overpriced) three wire type horn, the warning horn should beep once when the ignition key is turned to the ON position. If it does not, it is either faulty or someone has disconnected it (a stupid move!). At any rate, if it does not beep which indicates that the horn is non functional, find out why and do not run the engine until the problem is corrected.
Now that you are aware of what that horn is for, do this....... When the horn is sounding, remove the TAN wire from the horn. If the sounding continues, the horn is faulty.
However, if the sounding ceases when you remove that TAN wire, then at some point between that wire and the various alarm componets which in your case would be the "VRO Pump", the "Oil Tank", and the two "Heat Sensors" in the cylinder heads... a problem exists.
Ham Radio, the original wireless communications
Light travels faster than sound. This is why some people appear bright until you hear them speak!