Stock alarm on boxster

When I lock my doors using the button on my key, my lights flash twice and sometimes my horn beeps once. My horn doesn't always beep whenever I activate the alarm. Does anyone know why?

you have something open. when your alarm is armed you should not hear any beep. your alarm will beep if it sees the door open, front trunk open, rear trunk open, and glove compartment open. the micro switches in any one of these components might be bad. the biggest culprate is the front trunk and the glove box. unfortunately, you cant buy the micro switches seperate. you would have to buy the front trunk latch and/or the glove compartment lock/switch assembly.