Interior Light Wiring: How to Wire an Interior Light

FACTS CHECKED BY  Jose George​

The car’s interior lights help you see inside your vehicle during the night whenever you need. Further, modern cars have sophisticated and elegant interior lighting which works automatically. The electric connection is faulty if your lights remain ON when driving or even OFF when you open the door. This article contains all the required information about interior light wiring so that you can fix the problem.

Low Voltage Wiring
Low Voltage Wiring

What are the car’s interior lights?

Different interior lights in your cars help you read maps or see within the car. 

Dome lights

You can find these lights on the roof at the car’s center. Generally, the dome light bulb turns ON automatically when you open the door. So, if you see that the Dome lamp is ON, it indicates that one or more of your car doors are open. Passengers in the rear seat also use this light to read at night.

Map lights

As it is clear from the name, these two small lights on the car’s roof help you to read the map. One of these lights is on the driver’s side while the other is on the passenger side so that both can use the lights at their convenience. These lights also turn ON when the door is open. Apart from these map lights, there is another portable light near the rearview mirror.

Door lights

Most modern cars will have lights at the bottom of each door. When you open the door, these lights turn on so you can have a clear ground view while entering the vehicle.

Dashboard lights

You can view your gauge group like a speedometer with the dashboard lights. These multi-colored lights also help you prevent night blindness. 

Customizations 

Apart from these essential lights, you can also get some additional lights installed in your vehicle’s interior. You can opt for neon lights, fiber optics, or LED lights. These lights are long-lasting, cheap, less energy, and brighter than other lights. With these lights, you can express your style and taste and enhance the car’s usability.

Interior Light Wiring 

In modern cars, you will find wire circuitry that helps to switch on the lights when the door opens and switch off them in fading manner when the door closes.

Car Interior Light Circuit

Caption: Car Interior Light Circuit

Source: https://www.homemade-circuits.com/car-interior-light-fader-circuit/ 

door jamb switch wiring diagram

Caption: door jamb switch wiring diagram

Source: https://www.route66hotrodhigh.com/Relays.html 

The lamp connects to the battery’s positive terminal through a fuse, while the other end connects to the single-pole 3-throw switch.

When the switch is ON, the lamp connects to the ground or the battery’s negative terminal. As a result, the light illuminates.

The lamp connects to the ground through door switches (parallel) during the DOOR position. When you open the door, its corresponding door switch closes. On the other hand, in an OFF position, the lamp disconnects from the ground.

Inside lights not turning on: Causes and Fixes. 

With the car’s interior light circuit above, you can know the problem may be caused by Faulty dimmer switches, fuses, door switches, or interior lights.

Check the manual switch. 

Sometimes, somebody uses the lights and puts them in a state where they fail to turn on when the door opens. Based on the types of light wiring and the switches, you can try a different combination of buttons to turn the lights on. Try to rotate the dimmer; you may hear a clicking sound indicating whether it is in the ON or OFF position.

Suppose the dimmer or the dash-mounted interior light button is in a different position. In that case, you must try to operate the map, dome, and other interior lights with individual switches.

Change the blown fuses.

If all the interior lights stop working simultaneously and other things such as the radio are working, it indicates a problem with something the lights share in common. The root cause is a blown fuse or fusible links, so better check that first.

The cars have different fuse box locations depending on their wiring. However, you can find it in or near the glove box, in the engine compartment, or under the dashboard. In some vehicles, you will find more than one fuse box. So, it is better to take the car’s manual’s help when finding the fuse box.

Here the fuse you want is primarily the “lights” fuse; however, it differs from vehicle to vehicle. The best way to ensure the correct fuse is to look into the wiring diagram of the specific model and the year of the car.

At times, you can tell whether the fuse is blown or not by just looking at it. However, it does not always work. Sometimes, a blown fuse also seems perfectly fine. So, the best way is to check it with a multimeter. On checking with a multimeter, if there is no continuity between the two fuse terminals, it means it is blown.

Another easy way to test a fuse is with a test light. Clamp one end to any bare metal on your car and Touch the probe end to each side of the fuse. If the ignition key is in position, the test light should turn on when you touch both sides of the fuse. If the test light does not illuminate either fuse side, it means it is gone, and you must replace it. Make sure you take a similar fuse, as a more significant number can cause severe damage to your car wiring.

Problems with wiring

If the new fuse also blows out after replacing the blown a fuse, it means there is a short circuit. The shorts are often in those circuits in cars with map lights and door lights. Mostly, the shorts are at bend or crimp locations.

Faulty door switches

The last issue that can cause the failure of the car’s interior lights is a faulty door switch. These are called door jamb switches, as you can find them in door jambs. This door jamb switch opens when you open the car door, illuminating the lights and vice versa.

You can access the switches by prying off the rubber boot on it with the help of a screwdriver. Now, you can unbolt or unscrew the switch. Test the button with a multimeter by connecting its terminals and checking the continuity. Activate the switch and check again. If you see the same reading, there is a bad door switch.

Burned-out bulbs:

If one of the interior lights fails to illuminate and others are working fine, it indicates the problem of a burned-out bulb. You can quickly check this and fix it.

First, remove the interior light covering by unscrewing some screws. Look for several hidden clasps, also.

Remove the bulb also. You will have to apply a little force and do some twists to remove the bulb. Some bulbs are snapped tightly into holders, so you have to work more to remove them.

When you remove the bulb, take a test light and connect it to the ground and both the socket’s terminals. If the test light turns on, it means the bulb is bad.

You can still test the socket if you do not have a test light. Mostly, interior lights use similar types of bulbs. So, if you do not have a test light, remove a working bulb from another place and put it in the test socket. If the light illuminates, the socket is fine, and the problem is with the bulb.

Inside lights not turning off: Causes and Fixes.

Sometimes, lights stay on even when you close the doors due to malfunctioning.  You can try the following to solve the problem.

Interior light modules

If your car’s interior lights stay on for some time, even after closing the door, it indicates some problem with the timer module of the circuit.

If doors are not closed properly

One of the many reasons the car’s lights do not go off even after closing the doors is that one or more entries are not closed properly.

Fault in switch

As we said, lights function manually through various switches in the car interiors. So, if the lights are not turning off, check the manual control. You must have used it manually and forgot to turn it off. If not so, it may be possible that one or more switches are damaged, leaving functionality at the ON position.

Adjusting the dimmer switch to its highest position

There is a more undefined function for your car lights towards the left side of the wheel on the dashboard. When you set this switch to the furthest button, it will affect the car’s interior lights.

Conclusion

If your car’s interior lights do not function even after applying all the above suggestions, you should call a technician for help. Here, we at Cloom offer wiring harnesses and cable assemblies to make your car’s interior light wiring reliable and safe.

Get a free Cable Assembly Quote.