The other day I go to start up my caddy and it sounds like a dead battery. Take it out and have it checked and sure enough it's dead. I bring back my new battery and connect it and I turn the ignition and all the lights and dash work fine, but the car won't crank over. I take out the key circle the car, check everything then I go back in and try again but this time nothing turns on, no dash no nothing. As I go out again to check everything I hear a ticking sound coming from the driver side engine bay, it was the advert ignition relay (spelling). Take that out but my buddy says if it's making a sound that means it's working. We try to locate the starter to give it a good beating but we fail and we head out to grab some grub. I left my trunk locked but since car was not working the trunk was not completely closed. When we get back the trunk is completely closed. I run inside the car and try to turn her over but nothing. I noticed when I open the door all the lights in the car where flashing, they would dim and become very bright again. Throughout the whole day I have seen the little "security" light on my dash flashing. My buddy told me it had something to do with some type of security system on the car and since I have never replaced the battery that since it spent so much time without power I may need to do something. I purchased the car used and it came with a fairly new battery. Now I am here trying to figure out what is wrong with my car. This is my daily and I need to fix it asap. Any help would greatly be appriciated.