Taillights not working

Since I towed a trailer, my taillights have not worked and there seems to be a short in my headlights.
Experienced mechanics share their insights in answering this question :
Hi. There is a chance that the cabling got pinched somewhere while hooking up the trailer. Inspecting the cables thoroughly with a volt meter would lead to the area which has a fault. These lights are required by law and help to keep you safe while driving at night so this should be checked out soon. One of our certified technicians here at YourMechanic would be able to help you inspect for electrical problems and locate the cause of the issue.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

Electrical Issues

If you have a malfunctioning tail light, it could be a matter of a blown fuse. The fuses work with your car`s electrical panel and if they`re blown, it can cause several lights to stop working. Replace the fuse and see if this helps. Another issue may be related to your wiring.

There are actually a number of reasons why your tail lights could not be working but your brake lights are, including: Bad tail light fuse. Bad tail light bulbs. Socket failure.
Failing Sensor

If a sensor fails, it can interrupt this complex design and cause a part to stop functioning properly. If both the headlights and parking lights fail along with the tail lights but the brake lights keep working, a sensor is likely to blame.

Your rear lights are controlled through the same switch that controls the headlights. Power is channeled through a relay to the rear lights, illuminating them when the switch is engaged.
It is a 15amp fuse that powers the stop light switch on the brake pedal. The brake light switch sends power to rear brake lights.
Check the fuse.

A blown fuse usually causes both lights to go out. On newer cars, the tail lamps can be fused separately and/or each bulb or shared circuit can be fused. A fuse can be blown due to other problems, so you`ll need to check more than just the fuse, but it`s the right place to start.

Tail light relays are a vital part of any car on the road. Relays take out a manual aspect, or possibility for human error, in an electrical process. Tail light relays are linked to the headlight system of your car.
Bad Socket. If you have a single brake light out and the bulb is good, then the next step is to check the light socket itself. Brake light problems can include a socket whose connections are dirty or corroded or one whose wiring has become worn to the point where it`s only making an intermittent connection.
Tail lights are wired to the same switch that turns on the head lights, making them function easily. If you have automatic lights, the tail lights will turn on when your vehicle is on. If you use a switch to turn your vehicle`s lights on, the tail lights will illuminate once your head lights are on.
In North America, since 1986, all vehicles feature a third brake light. Legally, this is called the Center High Mount Stop Lamp, CHMSL for short, but informally called center brake lamp, high-level or eye-level brake lamp, cyclops brake light, or safety brake lamp.
You can see your brake light switch by looking under the dash, near the top of the brake pedal. The brake light switch is usually attached to a small bracket that holds the switch, activated when the pedal is depressed, in position.
A tail light in a shape of a LED bar with four E-approved functions – reversing light, indicator, brake light, and red position light approved as a tail light.
And because the taillights and brake lights do not share the same circuit, confirming the ground as a potential cause is not a task that needs much analysis.
A lighting circuit is protected by a 5- or 6-amp fuse or circuit breaker. This fuse size allows bulbs with a maximum combined wattage of 1150 watts (5 amps x 230 volts) or 1380 watts (6 amps x 230 volts) to be run off the circuit.
The brake light system is a simple on and off exterior lighting system which is controlled by a brake light switch located near the top of the brake pedal. A simple wiring circuit is connected to the car`s BCM and then onto the rear brake lamps (older cars do not use a BCM – body control module).
The main difference between tail lights and brake lights is that the former lights up as soon as the headlights are turned on, while the latter only engages upon stepping on the brake pedal. While both lights are red, brake lights tend to emit a more luminous red light.
Fortunately, tail light bulb replacement isn`t difficult and shouldn`t take you more than 45 minutes to an hour to complete. Be aware that newer models may be a little more complicated than older ones, as there will be more wires to disconnect.
Blown Fuse

A car fuse safeguards the tail light and brake light circuit from overcurrent. However, a high electric load on the rear light can cause a blown fuse and the tail light to stop working.

One of the most common situations that require the use of a relay occurs when an application needs to switch from high to low current (or vice versa) within the same circuit. For example, the temperature sensors that power HVAC units require levels of amperage that vastly exceed the capacity of their wiring.
Bad Socket. If you have a single brake light out and the bulb is good, then the next step is to check the light socket itself. Brake light problems can include a socket whose connections are dirty or corroded or one whose wiring has become worn to the point where it`s only making an intermittent connection.
If your car or truck has one headlight not working, such as one high beam or low beam not working, one tail light working, or the daytime running lights are not working on one side, there might be a problem with the bulb or the fuse.
The most common cause your brake lights stay on is because of a faulty brake light switch or sensor. It can also be caused by a faulty brake pedal or a malfunction in the electrical system. If you recently replaced the rear light bulbs when it occurred, you may have installed the wrong light bulbs.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

My dash board don’t work my front light work when I change my light into high beam and my back window won’t go down
ANSWER : As unfortunate as it is, your vehicle would be considered flood damaged. Diagnosing electrical problems in a flood damaged vehicle is nearly impossible. This would take many hours or even days to determine which wiring harnesses and circuits have been affected. Then nearly all of the wiring under the dash would likely require replacement as well as many sensors and switches. On a BMW vehicle, the amount of wires and switches are likely more than that of a lower end vehicle. Due to the inefficiency in cost, you would likely be able to purchase another BMW like yours for less than what it would cost to fix your car. Many insurance companies would consider this type of damage to total out the vehicle unfortuantely.

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Windshield wipers stopped working. They’ll suddenly stop working then suddenly start working again. Has been happening for a week.
ANSWER : The problem you are describing likely stems from an intermittent electrical fault in the wiper circuit. The windshield wiper system uses a small electric motor to move the wiper arms that you see on the windshield. That electric motor is controlled through a switch, relay, fuse, and wiring. One, or more, of those electrical components has failed although it is also possible that the mechanical arms are binding (seized, if the lubricant has dried out) thus causing the electric circuit to the motor to overload. Regardless of the underlying fault, if you request a non functioning wiper diagnostic/repair, the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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Dash, Tail/brake, dome, trunk, glovebox, and door lights won’t work, dash doing weird things.
ANSWER : Hi there. Sure would appear a lot is going on electrically all at once. This could be, a problem in the PDC (power distribution center). The PDC is typically located under the hood and contains numerous fuses and relays. I don’t believe any one fuse will resolve all of the electrical issues. There is a possibility, it is not a power supply issue. It may be, the result of a poor electrical ground common to the inoperative components. Proper circuit testing should be performed. This would confirm the cause of multiple electrical failures. I recommend having your vehicle’s electrical problems be diagnosed and repaired by a certified technician, such as one from YourMechanic.

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All dashboard lights and tail lights do not work after driving through a lot of snow. Headlights work. And brake lights work.
ANSWER : Hello. We’ll be happy to help you. There are a few things that I recommend checking to discover why your lighting system is malfunctioning. The headlight dimmer switch should be checked. Along with the wiring harness above the right front tire behind the fender well cover. Also
the main fuse under the hood should be inspected because other people with your particular vehicle have had similar lighting issues if that fuse goes bad. It will be a great idea to check the rest of the fuses in that area too while checking the main fuse. Once the fuses are checked inside of the main fuse box then I would check the fuses inside of their interior fuse box. The interior fuse box should be located on the driver side of the dashboard near where your legs would be. If you need more assistance with repairing your vehicle please keep in mind that our organization provides Mobile Mechanics who can help you diagnose and repair your vehicle, all at competitive rates.

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My AC does not always work. If I fiddle with the blower knob I can ususally get it to work on the lowest setting.
ANSWER : Hi There,
It sounds like you may have a faulty blower motor resistor. The highest speed setting may still work because in most cars in the highest fan speed settings the current bypasses the blower motor resistor. In some cars, if the resistor is failed, the fan may stop working completely. Another reason a blower motor resistor may fail is when the blower motor has a mechanical problem or when a foreign object jams the blower motor fan blade and prevents it from spinning freely. This leads to increased current through the resistor and causes it to overheat and fail. I would suggest having an expert from YourMechanic come to your location to diagnose your system to determine what may be causing the fan not to work properly.

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Honda Civic 2008. AC stopped working suddenly and engine check light came ON for a day.Next day AC worked and no engine light.
ANSWER : Hi there. In both cases, when an AC system is not working and a warning light is coming on the dashboard, typically a professional mechanic will complete the same initial inspection, which is to download the stored error codes that triggered the warning light initially. This tends to give them an idea as to what is causing the problems. This could be something as simple as an electrical relay that is faulty or loose or an indication of a computer related "glitch". Either way, the best way to move forward is to have a professional mobile mechanic complete a check engine light inspection.

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Okay so when I turn my lights on at night my brake lights do not work, when I don’t have my lights on they work fine.
ANSWER : Hi there. Based on your inquiry, it’s highly probable that you have a damaged light switch or some electrical fault inside the turn signal relay. However, it’s also possible that the brake switch above the brake pedal could also be the source of your problem. Due to the fact that multiple electrical components might be causing this issue, it’s a smart idea to first have a professional mobile mechanic complete a brake lights are not working inspection, so they can determine what’s causing all of these issues and recommend the right repairs.

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My headlights, blinkers, and brake lights work but the taillights, interior lights, and dash lights don’t work. All fuses, relays, and switches are good.
ANSWER : Hi there. There is either a break in the wiring on the lighting circuits for the main light switch or the ground wire to the main light switch for the running lights is loose or not hooked up. Check the wiring to the light switch and see if any wiring is loose or hot. If there is a loose wire, then the wire maybe the ground or a positive wire that feeds power to the lighting system. Fix any wiring that is loose and recheck the condition of the lights. You can try taking a jumper wire from the fuse box with the key on and to the power wire on the switch and see if the lights come on. If they do and the wire on the switch is tight and free of corrosion, then the light switch needs replaced. If you need further assistance with lights not working, then seek out a professional, such as one from Your Mechanic, to help you.

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