回答“car randomly wont crank. alternator, starter and battery good”Parasitic drain? Turn key off. Take oft positive battery cable. Take a DVOM and use the Amps setting. Plug the red lead into the meter's Amps terminal and the black lead in the common ( or ground ) terminal. Clip the black lead to the disconnected positive battery cable and the red lead to the positive battery post. I would hope not to have more than 300mA of current present. I think a half of an Amp is too much.