The light in the car does not go off

Is the light in the car not going off? Here you can find out the most common causes and what you can do before your battery fails.
The light in the car does not go off

When the lights in your car won't go out, it can be quite stressful. However, this is often caused by something fairly minor which can be quickly remedied. It is important that you stay calm and act quickly – because if the light is on all night, the battery could be flat the next morning and the car might not start.

If the parking light does not go off

Perhaps you once forgot to switch off the lights on your car in the evening. The next day the car could not start because the battery had discharged overnight. This can also happen if the lights in the car fail to switch off.

The time it takes for the battery to go flat depends entirely on which lights do not go off. High beam, fog and low beam lights consume the most power. When these are left on, the battery can be fully discharged in just a few hours.

If the interior lighting in the car does not go off, the load on the battery is much less than if the parking light were to stay on. Nevertheless, if the battery was not fully charged and the ambient temperature was low, then even low-level consumers like the interior or licence plate lighting can drain the battery to the point where the car refuses to start early next morning.

Permanent lighting in the car: possible causes

If the parking light or another car light no longer goes off, this could be for a number of reasons. But in almost all cases it is down to a faulty part. Finding out exactly what the component is often presents a difficult problem, even for experts. Possible causes:

  • Automatic light control
  • A broken switch
  • A faulty relay
  • Damaged or incorrectly routed cables

Automatic light control

In some European countries, such as Scandinavia, driving with a low beam is also compulsory during the day. Cars are therefore often sold with a lighting system that automatically switches on the low beam when the car is being driven. If you buy a used car with an automatic light system for example, the lights will go on whenever you drive. In this case, you should not worry that your car lights are permanently on.

Faulty switch

One of the most common causes of a car light not going off is a faulty switch. Although you have moved the switch to the "Off" position, the light does not receive the signal. This problem can usually be quickly detected by removing the switch.

Broken relay

A relay is a control unit in the electrical circuit that is responsible for closing circuits and, for example, switching on a light. If the relay stops working, although you turn the switch in your car to "Off" and the switch also forwards this signal, the relay remains in the "On" position and which means the light cannot be switched off. Replacing a faulty relay is a minimal cost. It is best to do this at a workshop.

Incorrectly installed or damaged cables

Cable damage and a subsequent short circuit and/or incorrect installation of cables can create a closed circuit in the car that is not connected to relays, switches and fuses of the actual circuit. The light may become connected to this "irregular" circuit because of a fault or damage – and as this circuit is not connected to the switch, you cannot turn off the light.

Important: If the light in the car does not go off because there is a fault in the circuit, then the light may stay on even once the fuse has been removed because the circuit was already closed before that.

If the switch or relay is not working and if you are not driving directly to the workshop you should first disconnect the fuse so that your battery will not discharge. But if there is a fault in the circuit, the light may remain on even if you remove the fuse. Then the only solution is to go directly to the workshop, or to disconnect the battery if the situation demands it.

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