How to Checking Battery leads and Connections

Checking Battery and Connections

A faint click or total silence when the starter key’s turned usually means the battery is nearly 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 in the least. 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 the other metal parts – they’re very corrosive.

If cleaning the terminals doesn’t cure the trouble, examine the earth lead – particularly where it’s attached to the body or chassis , and clean if necessary. There must be a bare-metal contact for correct earthing. Some cars have another earth lead between the engine and the body or chassis. make certain to look at it also. Look also at the starter and solenoid for loose connections, which may cause sparking. this is often a fireplace hazard in any circuit, but becomes a good greater one within the battery-starter circuit, which has around 300 amps flowing through it.

Make sure that the battery isn’t loose in its mounting, or electrolyte may spill over and cause corrosion. The battery leads also can 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 brief circuit.

Removing battery connectors

Clamp or cup connectors can be removed after unscrewing the securing bolt or fixing screw. But take care if the connectors have been tightly fixed on. Avoid prising them off or trying to twist them loose – undue force and damage the battery posts or their seal with the top of the case. A screwdriver can be used to force apart the jaws of a clamp connector.

The Ford type is removed simply by unscrewing its nut and bolt. Similar precautions should be taken when refitting. Do not hammer the connector down over the post. When you use a spanner on a clamp or connector bolt, take care to keep the free end away from the car bodywork, where it can cause a short circuit – even is the engine is switched off.

How to clean battery terminals

Use hot water and domestic soda to start out removing the powdery deposits which will form on terminals. But make certain that none of this solution finds its way into the battery cells. The battery posts can be ‘brightened’ with a wire brush or emery cloth. Do not, however, remove so much metal that the cup or clamp becomes a loose fit on the post.

If that does happen, some metal are often filed from the jaws of the clamp, or the sides of the cup can be squeezed during a little, in order that it grips the post once more. Alternatively, replace a cup connector with a clamp type.

Refitting the connectors

Smear a thin coat of petroleum jelly (not grease) on the mating surfaces of both the battery posts and connectors before refitting, to deter corrosion and ensure good conductivity. Ideally, the cup or clamp should be a simple push fit over the post. Tighten the securing bolt or screw enough to prevent the connector moving on the post, but don’t overtighten.

If a cup-connector screw doesn’t tighten because the thread has been stripped, put a length of solder wire into the opening to fill it partly. A self-tapping screw should then cut a new thread with enough bite to carry the screw firm. or just use a bigger self-tapping screw.


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