Your car’s headlights are an essential fitting. Even though they might not affect how the vehicle runs, they will have the final say on driveability when visibility dips or night kicks in.
Luckily, most headlights are specific electric components. This makes them easy to troubleshoot and fix.
What to Do When Your Headlights Stop Working
A couple of things could make one or both headlights to blackout. Doing a preliminary check while still in the cabin could help you narrow down the problem. Here is a list of things you should first do to help you get a better grip on the situation.
Are Other Electronics Working?
A complete electric system failure will of cause have an impact on your headlights. It is easy to be the culprit of general electrical failure, especially if your car is not on. First, ensure that other electronics like the car’s starter, interior lights, central locking and infotainment system are working.
If they are not, you could be dealing with:
- A fully depleted battery
- A blown main fuse
- A faulty ground strap
- Disconnected battery terminals
Are Both or One Headlights Off?
The next step is checking if one or more headlights have failed. If you have both headlights out, this could be a more centralized problem as the chances of the bulbs or LEDs on both headlights going out simultaneously are very low.
Localized to One Headlight
When the problem is localized, chances are you are dealing with a blown bulb or a loose connection.
Access the back of the affected headlight and check the fit of the headlight’s bulb harness. Clean and wiggle it to ensure it fits perfectly.
If this doesn’t fix the problem, you could first use a multimeter to confirm that the terminals receive power (12V) before getting a replacement bulb. Once you zero down on a blown bulb, order the correct replacement (halogen, incandescent, HIDs or LEDs.
Installing the bulb should fix your problem.
Both Headlights are Out
When both headlights are out, you should first do a quick check to ascertain if they’re both receiving power. You can do this by applying a multimeter to the respective bulb’s terminal with the lights on. Expect a 12V readout. If you can get it, you could be the unlucky few whose headlight bulbs blow out in pairs.
If you don’t get a voltage, the problem could be:
A Blown Fuse
Just like any other electric circuit, your headlights circuit ride on a fuse. In case of any fault, the fuse will blow, opening the circuit. In this case, your headlights won’t work.
- Consult your car’s manual to get the layout of your fuse box so that you can identify the correct fuse fast.
- Use nose tip pliers to pull out the fuse and inspect it. If it’s not blown, the problem is somewhere else in the circuit.
- If it’s blown, replace it with a new one of the same Amp rating.
Note that a blown fuse always hints at a problem somewhere down the system. Sometimes, the issues could self-correct – if it was a momentary failure when someone working on the car causes a short circuit.
In case the new fuse blows out again in a short time, you should have your wiring or the bulbs inspected since they might be overloading or short-circuiting the headlights circuit.
A Damaged Relay
If your fuse is OK, but the lights don’t work, you could be dealing with a damaged relay. Your car uses relays to switch the high current needed to power headlights instead of letting your switch on the stalk handle all the current.
Identify the headlights relay (mainly in the main fusebox or a secondary fusebox) and test it. If it is faulty, get a replacement and see if that fixes the problem.
A Faulty Dusk Sensor
Automatic headlights use a dusk sensor to detect ambient light and turn on the headlights when light conditions dip below the acceptable threshold.
If the sensor is faulty or blocked, your headlights won’t turn on automatically. Luckily most cars have a fallback manual switch. You can quickly troubleshoot this by manually turning on the headlights.
Should they turn on, then you will be sure that your dusk sensor is the problem.
A Damaged Headlight Switch
Finally, your headlights could fail because there is a problem with your headlight switch in the cabin. The switching stalk is in charge of so many things. While they are built to last, constant use could damage the contact.
Moreover, any recent work done on your car around the steering column could lead to accidental damage. Perhaps the mechanic tugged on the wrong wire disconnecting a switch position that controls the headlights.
Damaged Wiring Or Faulty Grounding
Broken or damaged wiring to the headlights could also take them out. If the +ve lead carrying power to the headlight bulb is cut or disconnected at the terminal, your bulbs won’t get any power. This isn’t as common. Common failures include:
- Frayed insulation will make the cable arc to the ground hence blowing a fuse
- Loose terminal or connectors
- Someone left the light unplugged or accidentally cut a cable when working on the car.
Your headlight will also need a connection to the ground a.k.a. the car’s chassis. Confirm that the negative terminal of the headlight is wired to the ground. If all other electronics in the car are working, you shouldn’t have ground problems and the headlight’s negative terminal connection is the only issue.
Is it the Low Beam, High Beam, or Both?
Another quick way to confirm if it’s a blown bulb is checking if the other bulbs are working.
Try the high beam if the common beans are not working and vice versa. If one of the positions work, chances are you’re dealing with a blown bulb.