A faint click or total silence when the starter key is turned usually means that the battery is almost or completely flat. If, however, the battery is fully charged, the trouble is probably in the circuit between the battery and starter.
Either way, lack of power is preventing the starter motor from working – though there may be just enough current to work the solenoid, which makes a faint click or chatter.
If you suspect the circuit, look first at the battery-terminal connections. Unless they are in good condition, the current cannot flow through them properly – and sometimes not at all.
The most common types of connector are a clamp that fits around the battery post, or a cup that fits over it. The clamp is secured by a bolt; the cup by a screw into the top of the post.
The Ford type has a flat cable connector bolted to a flat battery post.
The mating surfaces of both connectors and battery posts must be free from dirt and corrosion.
Any green or white powdery deposits must be removed, and the metal surfaces beneath brightened.
Remove these deposits also from the battery carrier or any other metal parts – they are very corrosive.
If cleaning the terminals does not cure the trouble, examine the earth lead – particularly where it is attached to the body or chassis, and clean if necessary. There must be a bare-metal contact for proper earthing.
Some cars have another earth lead between the engine and the body or chassis. Be sure to examine it also.
Look also at the starter motor and solenoid for loose connections, which can cause sparking. This is a fire hazard in any circuit, but becomes an even greater one in the battery-starter circuit, which has around 300 amps flowing through it.
Make sure that the battery is not loose in its mounting, or electrolyte may spill out and cause corrosion.
The battery leads can also work loose, or the case may crack through being bumped about. A loose clamping bracket can touch the live terminal of the battery and cause a short circuit.