Last Updated on April 2, 2022 by Bernard Juchli
The reasons lights won’t turn off in a car depend on the light – headlight, interior light, brake, etc. Thus, each light may have a similar, or distinct cause.
Suppose you drove home, parked the car, turned the lights off, and went inside only to discover a few minutes later that the lights are still on. It could be the head, interior, or tail light, but whichever is on is draining the battery.
The first thing you want to do is to disconnect the battery to stop the drain. The next is to determine the cause of the light and fix it.
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Reasons interior car lights won’t turn off
Below are the reasons why the interior light of your car will not turn off after you off the car:
Door not fully closed
If you have a modern car, the interior light could be on because the door is still open. This is because the light is linked to the car door, and sometimes the trunk, also called cargo.
Whenever you open the car door, the interior lights up somehow. Even the dome light may light up in some cars.
An activated control knob
If the control knobs are active, the interior light of the car will light up even when you turn it on. This is typically the case when your dome light will not turn off.
This happens when the control switch is stuck. You can tell if the control knob is the problem by trying to adjust the brightness of the dome.
However, if the interior light brightness remains despite turning the dome light switch, the switch is broken. If you do not want to disconnect the battery, disconnect the bulb to avoid draining battery juice.
A faulty switch
Your interior light not turning off could be due to a switch problem. The manual switch on the dashboard, roof or door could be faulty. In mild cases, it could be that you forgot to turn off the switch.
The interior light of your vehicle is likely to stay on if the dimmer adjustment is set to the highest.
The interior light dimming function is typically located on the left side of the wheel next to the dashboard. If the setting is at the furthest position, the interior light could be affected.
Fixing interior light not turning off in car
Adjust the switch
The first step is to try to turn off the switch. You or another passenger may have accidentally turned the switch on. Just turn it off and see if the light won’t go off.
Inspect the headlight switch setting
If the knob controls the dashboard light brightness in your car, make sure the settings is not on the highest. This will stop the interior light from turning off when you off the car.
Inspect the door/trunk light switches
The interior light switches on the doors, and in some vehicles, the trunk could be the solution to your interior light not turning off. Check the switches on the doors or even the trunk, depending on your car.
Try to open and close all the doors and the trunk to check if the interior light will turn off. If the light stays on, use the manual switch on the door (if any on your car).
The manual switch should produce a click sound when you press it. If there is no click sound, and the interior light will still not go off, the door switch may be faulty. See a technician to replace the switch.
Reasons headlights won’t turn off in car
The headlights in your car will not turn off if:
Engine timer is faulty or dead
If you shut off the engine in certain cars, the headlights stay on for some time before fully going off.
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If the headlights continue to stay on after more than 3 minutes, then the engine timer is faulty. It could be misreading the time or not working at all.
To confirm if the engine timer is the culprit, shut off the headlights before you turn off the engine. If the headlights turn off, the timer is faulty.
Faulty automatic headlight
The headlights turn on automatically in some cars, typically depending on the amount of external light. If this auto light system fails, the headlights of your car will get constantly stays on. To confirm this problem, use the parking brake to check if the headlights will go off.
The parking brake may be able to disable the automatic light features. If the parking brake turns off the headlight, the problem now points to the automatic light system.
Damaged headlight relay
A damaged headlight relay will prevent the headlight from turning off. This means that your vehicle system is sending the wrong relay information, causing the headlight to be stuck.
You can locate the relay system under the hood of your car. Its function is to signal to the headlight determining how long they will wait to turn off.
Tap the relay to see if it is the cause of the problem. The light should flicker and or shut off if the relay is the cause of the headlight not to off.
What if only one headlight turns off?
If one of the headlights will not turn off, a faulty automatic light could be responsible. The headlights can stop syncing, such that one responds by turning off while the other is still on. Try to use the parking brake to test this theory.
If both lights shut off after you use the brake light, the automatic system just failed to sync the lights. Also, the headlight burning out can cause only one light to turn off.
Fixing headlight not turning off
The fix below depends on the cause of your car headlight not turning off.
If your headlight relay is damaged, and the reason your headlights won’t turn off, have the relay replaced. Many circuits in your vehicle may be using the relay, so it is easier to check.
However, if your car uses another relay with the same part number as the headlight relay, remove the headlight relay, and swap it with the identical relay from another circuit. The headlight should now turn off, but if it does not, buy a replacement relay.
Faulty headlight switch
If the headlight will not turn on after switching the headlight relay, the headlight switch may be faulty. Even the light sensor could be the reason your headlight won’t turn off. Unfortunately, the diagnostic procedure for the light sensor is a bit complex.
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Try removing the device to check for physical damage such as a crack, melt or burn. Note that not spotting any physical indicators on it does not mean it is not faulty.
Remove the headlight relay
If you have to fix your headlight not turning off, remove the fuse or relay. This alternative is a bit complicated, at least more than disconnecting the battery. The reason is that you may not be able to find the correct fuse panel to figure out the correct fuse or relay to draw out.
This will prevent power loss to the computer and radio. However, you do not get to deal with any fallout later.
Reasons brake light won’t turn off
Like other lights, there are a few reasons your brake light stays on after you turn it off. Below are the reasons:
Faulty brake light switch
A faulty brake light switch at the brake pedal lever can be the reason the brake light will not turn off. However, the switch may still be moving correctly when you match the pedal but do not turn off the electrical signal illuminating the brake lights.
A faulty brake light switch is quite an uncommon reason for brake lights staying on. It does not mean it cannot get damaged.
The plunger of the brake light switch is designed to contact a plastic/rubber bumper on the brake pedal lever on some vehicles. This bumper can fail, and without it, the switch plunger extends, which illuminates the brake lights.
If you find this small plastic/rubber below your feet, and your brake lights are not turning off, the failed bumper could be the problem.
Faulty CAN Bus System
A failed CAN (Controller Area Network) bus system can cause your brake light not to turn off. CAN in a car is a message-based protocol that allows the ECUs (Electronic Control Units) and other devices to communicate with each other.
Stepping on the brakes
Your brake light could be staying on because your foot is still slightly pressing it. You typically rest your feet lightly on the brake pedal while driving.
However, the slightest pressure that moves the pedal will turn on the brake lights. Make sure that the object is resting on or adding pressure to the pedals, then check if the light turns off.
How to fix brake light not turning off
Replace the switch
Replacing the brake light switch will stop the lights not turning off when you do not press the brake light. You need a mechanic to make the necessary replacement since it involves complected procedures.
CAN bus diagnosis
A hardware or software problem can stop your brake lights from turning off. Have a professional diagnose and correct the system problem.
Reasons parking light won’t turn off
Below are the reasons your parking light will not turn off:
A fuse protects the electrical components of your car from surges. And fuse malfunction will prevent the parking light in your car from turning off.
A fuse is built to cut off the power supply when the electric current passing through them is excessive. This could cut off the commands to your parking light to protect the entire circuit.
Dead parking light switch
A malfunctioned parking light switch will cause the light to stay on even if you turn off the engine.
Nonetheless, your parking light switch may be working, except that you forgot to turn it on since you do not use it frequently. An engaged switch will turn on the light even with the engine turned off.
Disabled automatic parking light feature
If the auto-on-off feature is faulty, your parking light will remain on when you turn off the engine. It serves as a sensor that turns on/off the light in your car.
When you turn off your car engine, you basically trigger a sensor that should automatically turn off the parking light. If the light does not go off, this sensor could be faulty.
Power feedback from other systems
It is possible for the power feedback from another system to stop the parking light from turning off. To confirm this problem, you would have to go under the hood of the car. Remove each of the fuses until you find the fuse that controls the light.
A wiring malfunction or short circuit will be the culprit behind your parking light refusing to turn off.
It is typically challenging to tell as there are many components in the vehicle with running wires. Just any broken wire should be thoroughly checked.
Stuck turn signal relay
If the turn signal relay sticks in one position, the parking light will not go off. The turn signal relay controls the signals, including turning them off and making sure they are safe for driving.
Steps to fix parking light not turning off
Restart the system
Repeatedly start the car for a few minutes and turn it off again for some time. This can help to clear minor glitches that could be causing the parking light not to turn off.
Disconnect the car battery
Disconnect the car battery, and allow it to sit for up to 15 minutes before replacing it. This action cuts off power from the car, including electrical feedback that may be stopping the parking light from turning off.
Disconnect the fuse
If disconnecting the fuse does not stop this problem, check the connectors or wiring for shorts, damage, or loose connections. Try to test all fuses to know if they are functional. Replace any faulty fuse or wires to fix the problem.
Contact the mechanic
The mechanic is your last resort if you cannot tell the reason or fix your lights not turning off in the car. A professional will diagnose the vehicle for bad sensors to fix the light problem. Ensure to make any necessary replacement to stop the issue from developing into major damage.