1994 G20 Security

[shaguna]

I've purched a 1994 Infiniti G20 in march and it has been sitting in parking lot for the most of the time. If not used for a few days, the battery will die. After jumped-started, the alternator will charge the battery and it will hold the charge for another few days. The "security" light keeps blinking after removing the key from ignition, using the remote will lock the doors but the light keeps blinking. I did replace the fatory stereo with after market mp3/hd radio unit. Could this be the problem ?