My 1985 Nissan 300ZX manual 5 speed non-turbo digital won't turn on. First of all, the security light is always blinking before and after I open/close door. Car won't even turn over.

Yes...get a NEW battery...modern batteries have NO LEAD in 'em and are tin/antimony alloy...will last but five years before they stop takin' charge readily...so get a NEW one...to make sure that you're not "locked up" like after a catastrophic overheat, get a jumpstart...if it still will not turn over, try to turn the engine...make sure that it will turn...okay next there is a 1/0awg Cable leading to the motor block...make sure that the engine is grounded~ I've been told that if you hold the tripodometer, while off and "on" five times will clear the computer and remove the beeping~ just a rumor, but worth a shot~