some replies to your comments:

SoAm ( at least Venezuelan ) cars didn't have the interlock system... I just got from USA cars since I'm "cloning" for a complete 74 USA car with all real stuff, nothing bypassed.

So, to your thoughts, nothing is bypassed, cut or modified simplye because just recently I made the installation and worked at first instance. Simply suddenly one day stop to work like it should be.

The fact you don't like interlock doesn't mean I can get it working as must be

I made all testing explained on FSM manual ( I got emailed that section ) and everything takes me to a damaged control unit, but just partially because the logical circuit what makes work the warning signals is working like a clock, buzzing/lighting when I try to crank and when I gear. Just that shouldn't crank, but is cranking. I have been analizing the printed board inside interlock and does look could it be a diode or transistor went bad. There is a BIG transistor what links the starter circuit. Have to seartch further thought.

I say the logical circuit, including sensors, is working perfect simply by the fact all sensors are sensing... seats, buckles, making work the light and buzzer on the right moments.

BTW what I have experienced with interlock system and if everything was good in the fisrt, as far seats sensors doesn't send signal, you can crank engine, so for a fast start up, simply start before sit