Siren alarm going off but it's not the burglar alarm

Hello. my 2004 Hyundai Elantra GLS has an alarm that won’t go off until the car is started and running or the negative battery cable is disconnected. The technician at the Hyundai dealership is baffled on this one. If I press the panic alarm button on the key chain, the alarm gets very loud. When the panic alarm is turned off, the alarm is quieter. The keyless entry won’t work at all now. Does anyone have any ideas short of dynamite?

I am going to assume that you bought this car as a used car, rather than a new one.
If, as I suspect, that is the case, it is fairly obvious that a previous owner installed an aftermarket alarm system.

However, dealerships are not usually familiar with aftermarket alarm systems. You need to go to the best independent shop in your area that installs aftermarket alarm systems.

Good luck. This may be a difficult one to track down.