Understanding dashboard warning lights and what they mean

Modern cars are covered in warning lights, and they are not there to decorate the dashboard. Each one is a message from a system that has something to say. The colour tells you how urgently you need to act. On West Country roads, where a lay-by can be miles away and mobile signal is patchy, knowing the difference between a red light and an amber one is genuinely useful. Here is what the colours mean and how to respond without panicking.

Red warning lights: stop safely and investigate

A red light is the car telling you to stop as soon as it is safe. Do not carry on to the next services or wait until you get home. Pull over, switch off the engine and assess the situation.

• Oil pressure — an oil can symbol. Stop immediately. Check the oil level when the engine is cool. Driving with low oil pressure can destroy an engine in minutes.
• Coolant temperature — a thermometer in liquid. Pull over and let the engine cool before checking the coolant level. Never remove the cap while the system is hot.
• Brake system — a circle with an exclamation mark, or the word BRAKE. It could be the handbrake left on, low fluid or a serious fault. If the pedal feels soft or sinks, do not drive.
• Battery charging — a battery symbol. The alternator may have failed. You might have limited range, so turn off the radio, heating and lights, and head to a garage.
• Airbag or SRS — the airbag may not deploy in a crash. Drive cautiously to a garage; this is not a roadside fix.

On narrow Devon or Somerset lanes, find a gateway or lay-by rather than stopping on a blind bend. Safety first, diagnosis second.

Amber warning lights: attention soon, not panic

Amber means something needs checking soon. The car is usually drivable, but ignoring an amber light can turn a cheap sensor into an expensive repair.

• Engine management light — an engine outline. If it is steady, book it in for diagnostics. If it is flashing, stop safely; you risk damaging the catalytic converter.
• ABS — anti-lock braking is disabled. Normal brakes still work, but you lose emergency braking assistance. Leave more space, especially in the wet.
• Traction control or ESP — often appears with ABS or on slippery leaves and mud. If it stays on, get it checked.
• Tyre pressure — an exclamation mark inside a horseshoe. Check pressures when tyres are cold. Cold snaps often trigger false alarms, but repeated warnings mean a puncture or a failing sensor.
• Diesel particulate filter (DPF) — short trips around town clog it. A steady run at motorway speed can help if your handbook allows it. Otherwise a garage can force a regeneration.
• Glow plugs — common on older diesels in winter. Rough starting and smoke are clues. Fix it before the cold arrives.

Treat amber as a to-do list. Note what you were doing when it appeared — braking, accelerating, climbing a hill — and tell your garage.

Green and blue lights: systems doing their job

Green lights simply show that a system is active. There is no fault. Blue lights usually indicate main beam or fog lights.

• Green — indicators, sidelights, headlights, cruise control, lane keeping assist, start-stop, and the ready light on many electric vehicles.
• Blue main beam — dip promptly for oncoming traffic and when following other vehicles.
• Blue fog lights — use only when visibility is seriously reduced. Switch them off as soon as conditions improve; they dazzle other drivers and can be illegal otherwise.

Do not confuse a blue fog light with main beam. Both can be irritating, but fog lights in clear weather are a common cause of glare on dark country roads.

If a light comes on while you are driving

Stay calm, check your mirrors and indicate before pulling over safely. A red light means stop as soon as possible. An amber light usually lets you continue to a garage or home, but drive gently and avoid heavy loads or long climbs.

• Check the handbook for that exact symbol. Shapes and colours vary between makes and models.
• Note the conditions: were you braking, accelerating, going uphill or just after refuelling?
• Do not disconnect the battery or tape over the light. You will hide a real fault and may fail an MOT.
• If you are unsure, call a breakdown provider or a trusted garage. On a West Country road trip, do not gamble on a remote stretch of the A39 or a moorland road after dark.

West Country ownership: salt, hills and short trips

Coastal air and winter salt accelerate corrosion on sensors, wiring and brake pipes. ABS and brake wear lights are common on older cars kept near the sea. Hills and towing add heat to brakes and coolant, so a temperature light that flickers on a steep climb deserves attention. Short trips around town clog diesel DPFs and trigger amber warnings. Electric vehicles have their own set: battery temperature, charging faults and 12-volt battery warnings are worth understanding. Regenerative braking can also mask worn brake pads, so get them checked even if the car feels fine.

If you are buying or selling, warning lights matter. A dashboard lit up like a Christmas tree is a bargaining chip or a deal-breaker. Fix lights before advertising a car, and when buying, check that every light illuminates with the ignition and then goes out. A seller who says “it is just a sensor” may be right, but verify with a code reader or an inspection. Before a road trip to Cornwall, Devon or the New Forest, check your fluids, tyre pressures and know your red and amber symbols. A little knowledge keeps you moving.