Car electrical problems: lights, alternator, starter motor

Battery, alternator and starter motor, explained#

• The battery supplies the current for starting and for anything that runs with the engine off. It discharges and wears out over time. The signs of a battery near its end are in our car battery guide.
• The starter motor is an electric motor that turns the engine for a few seconds when you start. It draws a lot of current, which is why a weak battery shows up first when starting.
• The alternator is driven by the engine through a belt and produces current while you drive: it charges the battery and powers the lights, the fan and the control units.
• Fuses, relays and wiring connect it all. A blown fuse cuts a single circuit, for example one window or a power socket.

On many cars with stop-start, a system monitors the battery's charge, and a new battery has to be registered in the car's computer with a diagnostic tester.

Signs of an electrical problem and what they may mean#

When a warning light comes on, the computer has usually stored a code. The auto electrician reads it during a diagnostic check and then traces the cause with a meter: the code shows where to look, not which part to replace.

If you smell burning plastic or see smoke from the dashboard or under the bonnet, stop safely, switch off the engine and get out. Don't start it again until an electrician has seen it; call roadside assistance.

The car won't start: what to do#

1. Look at the dashboard when you switch on the ignition: if the lights are dim or don't come on at all, the battery is flat or a terminal has come loose.
2. Listen: rapid clicking usually means a weak battery; a single click with the dashboard lights normal may be the starter.
3. Don't keep cranking for minutes on end: you'll drain the battery completely and overheat the starter.
4. Jump-start from another car only as the manual describes: some cars have dedicated connection points, and a mistake can damage the electronics.
5. Call roadside assistance if your policy includes it, or if you're not sure what you're doing.

If the car starts with jump leads but not again the next day, have the battery or the alternator checked: a test at the garage shows the battery's condition and the charging voltage.

The lights and the ITP#

The lights are checked at the ITP (Romania's periodic roadworthiness test): the headlamps and their aim, indicators, brake lights and side lights. The EU directive on periodic roadworthiness tests (2014/45/EU), which Romania has written into its ITP rules (RNTR 1), classes these, among others, as major deficiencies:

• A headlamp whose colour, position, brightness or marking doesn't meet the requirements.
• A headlamp whose only light source has failed, or whose reflector and lens are badly damaged.
• Wiring that is badly deteriorated or poorly secured, touching sharp edges or with connectors likely to come apart.

A major deficiency means a fail; see what is checked at the ITP. Fit bulbs of the type given in the manual: a bulb or kit not designed for your headlamp can take it outside the requirements.

Why add-on wiring causes trouble#

Alarms, dashcams, audio systems, tow bars or extra lights fitted after the factory are wired into the car's electrics. Done in a hurry, with twisted wires and insulating tape, without their own fuse or on the wrong circuit, they can cause faults that are hard to track down:

• A flat battery overnight, from a device that doesn't switch off with the ignition.
• Error codes and warning lights: the modules in modern cars talk to each other over data networks that are sensitive to tampering.
• Corroded contacts and faults that only show up in the wet or over bumps.
• Overheating, if a wire that's too thin feeds a heavy load.

For any add-on, go to an auto electrician who works from the car's wiring diagram, with a separate fuse and proper connectors, and keep the invoice. If the car has add-ons of unknown origin, tell the electrician from the start.

What to ask the auto electrician#

1. What they measured: the battery's condition, the charging voltage, the drain with the car switched off.
2. Where the fault is: in the part or in a connection.
3. What your options are for the alternator or starter: new or reconditioned, and the warranty on each.
4. Whether a new battery has to be registered in the car's computer.
5. What warranty they give on parts and labour.

How CariX helps#

In the free driver account you have what you need to hand when the car lets you down.

• Roadside assistance: add the assistance number from your RCA (compulsory third-party insurance) or CASCO (comprehensive) policy, if it includes assistance, and it sits on the car page, ready to call.
• "Is the price fair?" shows an indicative price range for electrical work in your city, from the prices businesses list on CariX on their pages and quotes; the real price depends on the car and the parts.
• Warranties: if the garage records a warranty on the job line, for example on an alternator, you see it under "Active warranties" on the car and get an email 30 days before it ends (for a warranty in months).
• The ITP with a reminder: you pick the inspection date and the validity, and CariX emails you 30, 14 and 7 days and 1 day before, so you can check the lights in good time.