Re: Car doesn't start?
That's what I meant by "black box", the starter motor is where they show a ground and the box is really the solenoid.
If the solenoid is going click-click-click then the problem is on the left. What happens is the solenoid is an electromechanical device. When the switch is turned 12v travels down the chain on the right to the solenoid where a big electromagnet (pulls about 10A) pulls in the bendix drive so that it engages the flywheel. The last fraction of an inch makes a big contact that applies 12v to the motor.
The initial surge to the starter motor can exceed 100A and if anything is chancy particularly in the battery the 12v can suddenly drop to 6v or less (normally the drop is to 9-10v and there are special circuits to make sure the ignition is kept up).
However if there is a problem the voltage can drop below 6v and this is not enough to keep the solenoid energized so it drops out, the load drops, voltage returns and the solenoid tries to pull in again.
This is why a weak battery will often go click-click-click-click instead of turning over.
Also why exactly where that reported "click" is coming from is important.