One Headlight Goes On And Off

One Headlight Goes On And Off: Why and How to Fix?

If you are having an issue with your car’s headlights and it continuously goes off and on, then there may be a fault in the bulbs of the headlights. This common issue can happen for many reasons, such as a fuse, headlight relay, issues with the switch, etc. 

Apart from it, there also can be a wiring issue of your headlight that may be causing the fault in the headlight.  

So there can be an issue among the above, and it is necessary to find out the cause of the fault in the bulb to start repairing it. Therefore, it is better to take your car to the mechanic to properly diagnose and repair it whenever you suffer from a similar problem.

Table of Contents

Why Does My Headlight Keep Going On And Off?

There can be several reasons your headlight can start going off and on. So do not worry; today, you will learn all about it so that you can immediately look for the cause to fix it as soon as possible. 

The headlight can show this misbehavior due to a broken or blown fuse, or there can also be an issue in the bulb. There can also be a wiring issue that is causing the headlight problem.

One Headlight Goes On And Off
  • Fault in Relay Switch

If there is any problem in the power that passes through the relay switch, then it may cause the lights to come on and off frequently. 

So check whether there is any loose connection or wiring issue inside the headlight assembly due to which your lights turn off? Your light assembly may have any fault, such as bulb sockets.

  • Fault in Head Light Switch

After checking the relay switch, now check the headlight switch. The switch can be faulty if worn or out of order, or you see your lights blinking or turning on and off frequently. You can test the switch by plugging back and forth into the socket.

  • Fault in fuse

If there is a faulty fuse, then it can cause the headlight to start going on and off. So what you do is to check the fuse and replace it if needed. 

However, the fuse can be burnt due to too much load on the circuit, or there can be another reason. So you should look for the broken fuse if you want to fix this headlight problem in the shortest possible way.

  • Fault in bulb

Your headlight may not be working correctly if no light comes out of the bulb. There can be two reasons for that: breakage or a fault in the electrical connection within the bulb. 

You should diagnose it first and then repair it or perform some tests to confirm your diagnosis with other means.

  • Fault in the wiring

If there is no light at all when you open your headlight, there could be a voltage problem causing overheating within the lights. If it is not a lighting problem, there could be a malfunction in the housing, which can cause high power consumption or airflow issues.

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How Do I Know If My Headlight Relay Is Bad?

There are multiple signs and symptoms through which you can know if your headlight relay is damaged or not. 

How to Diagnose a Failed Relay In Your Car, Truck or SUV

Here are some of the signs and symptoms of a bad headlight relay:

Headlight won’t turn on:  If your car won’t’ turn on, you should know that there may be a problem with your headlight relay. When the relay is dirty and corroded, it will not be able to send power to the headlamp unit.

Headlight won’t turn back off: It is another problem where once you turn on the headlight, it won’t turn off whether you try to switch it off. This problem can drain the battery during the daytime when you do not need the headlights.

If you want to check your headlight to work appropriately whenever you take it out for a night drive, then you should know these signs to maintain them properly. 

So look out for the signs and symptoms, and whenever you notice them take your car to a professional to fix it before any further damage.

Why Does My Low Beam Keep Going Out?

If your low beam bulb keeps going out, it may have a housing problem, damaging the headlight bulbs. If you have replaced the headlight, but it too has got an issue, there’s a chance it was not installed correctly.


Thus multiple causes can lead to the issue of the low headlight beam going out.

Improperly installed bulb: You may have replaced the bulb, but it was installed improperly and was not correctly aligned with the center mark.

Headlight housing loosens: You should check the vehicle from underneath very carefully. If the headlight looks loose, then it is likely that they are getting weak due to the heat and age of the components. 

Lack of tension in assembly: The assembly may have no tension in it, preventing it from staying tight, cushioning, or allowing your headlight to be loose and fall out, thus releasing pressure to the bulb, causing its failure. 

Leak or temperature problems: The bulb may have temperature issues such as melting, dripping, or corrosion causing it to leak and dissolve into the housing, resulting in the destruction of your bulb.

This can happen because you’ve done something wrong and not noticed yet, or it could be due to someone else replacing the bulb and not making sure it was correctly installed.

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How Do You Fix A Headlight Relay?

It is seen that most of the headlight issue is caused by bad headlight relay. Thus, if you have checked and are sure that the relay is causing the headlight issue in your car, then it’s time to replace and fix the problem. 

You can use these below-given steps to replace the relay to fix the headlight problem in no time:

  1. The first step is to locate the headlight relay. Open the car’s bonnet and get down to the engine bay to locate the relay. Next, locate the fuse box and remove it from its place.
  2. Open up the fuse box and locate the headlight relay. The headlight relay is shaped like a rectangle box with three wires coming out of it.
  3. Now comes the most challenging part, removing the old headlight relay. Since it is mounted in the fusible box, you have to remove the old fusebox to replace it.  
  4. Start removing the old relay from the fusebox by slowly pulling wires out.
  5. You might have to remove wires from the connector to remove the headlight relay. It is much easier if you use a wire cutter to cut the wires instead of using needle nose pliers.
  6. The tricky part is connecting the new relay with wiring back into its place. It would be best if you made sure that all the wires are connected correctly, i.e., Positive, Negative, and Signal, or else it might temporarily damage your car.
  7. Now it’s time to re-installing the new headlight relay into a power source, and that’s it. This is how you can fix your headlight relay in easy and simple steps.

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