Haynes seriously useful info

The Seriously useful info series

Although many car owners believe that modern cars are too complicated for them to work on, this is not so. Routine tasks can be done by anybody - if they know what they are doing.

With the Seriously Useful Info series, our mission is to give you a greater understanding of your car and provide you with essential tips, advice and tasks that will aid trouble-free motoring. For example: how to check tyres and engine fluids, replace wiper blades, light bulbs and spark plugs, how to conduct a pre-MOT test check and what to do before taking your car on holiday or abroad.

Links to the other Seriously Useful Info features appear at the bottom of this page.

How To Use Jump-Leads

Haynes Car Maintenance - Jump Leads Few things are more dispiriting than turning the ignition key and hearing nothing. Just when you need your car to start, it plays dead. Worse still, it's probably your fault. Look at the lights switch - did you leave them on?

Modern car batteries are very reliable, but leaving the lights on for a few hours will soon discharge them. Even a boot light or an interior light left on overnight can flatten a battery. And a car left standing for a month or so may discharge its battery just from the current drawn by the alarm.

There are other causes of a flat battery - the charging system may be faulty or the battery may simply be worn out. But whatever the cause, the tell-tale signs are headlights that fail to come on or just glow dimly, and an engine that turns slowly or not at all when you rotate the ignition key.

Haynes Manuals list the battery in the section on weekly checks for your vehicle. This is astute advice, because battery failure is one of the commonest reasons for calling a breakdown service. Haynes is the world's leading publisher of automotive repair manuals and renowned for teaching millions of car owners how to carry out routine maintenance and repairs. Haynes publishes manuals for more than 500 cars and vans.

To start a car with a flat battery, you need a friend and a set of good quality jump-leads. A friend with a set of good quality jump-leads is better still! Your friend must have a car with a battery in good condition, and jump-leads - heavy-duty cables with beefy clamps at each end - are available from good car accessory shops. To jump-start your car, simply follow the instructions below. Do remember that fully discharging a battery will reduce its life - don't be surprised if it needs replacing sooner than you expected.

Haynes, the world-leading publisher of automotive repair manuals, is renowned for teaching millions of car owners how to carry out routine maintenance and repairs. The manuals provide authoritative and accurate step-by-step information for both basic and more complex tasks.

For more advice on model-specific procedures, please refer to the appropriate Haynes Service and Repair Manual. Haynes Manuals are available from this website and all good car accessory retailers and bookshops including: Halfords, Motor World and WH Smith. Please use our comprehensive Stockist Locator in the left margin of this page.


1. Position another car near yours so that the batteries are close, but do not let the vehicles touch. Switch off the ignition and all electrical equipment on both vehicles, apply the handbrakes, and ensure that the gears are in neutral (manual transmission vehicles) or 'P' for automatics. Open the bonnets.
2. Connect one end of the red jump lead to the positive (+) terminal of the flat battery - do not let the other end of the red lead touch any vehicle metal - and connect the other end of the red lead to the positive (+) terminal of the boosting battery.
3. Connect one end of the black jump lead to the negative (-) terminal of the boosting battery and connect the other end of the black lead to a bolt or metal bracket, well away from the battery, on the engine block of the vehicle to be started.
4. Ensure that the jump leads cannot come into contact with any moving parts of either engine. Start the engine of the boosting vehicle and run it at a fast idle speed. Now start the engine of your vehicle and check that it is running properly.
5. Stop the engine of the boosting vehicle only. Switch on the lights, the heated rear window and the heater blower motor on your vehicle - this is to prevent any voltage surges. Disconnect the jump leads in the reverse order of connection, then switch off the lights etc. Close the bonnets.
6. Now you can drive off. It will take a little time for the alternator to charge the battery fully, so don't stop the engine again too soon and try not to stall it while driving!

Seriously useful info features....

'Haynes Publishing' is the trade name of JH Haynes & Co Ltd ( Company Number 1449587 ). Both this company & its parent company, Haynes Publishing Group P.L.C. ( Company Number 659701 ), are registered in England & Wales and their Registered Office is at Sparkford, Yeovil, Somerset, BA22 7JJ, England.