How to test a headlight bulb with a multimeter (guide)
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Finding out that your headlight has stopped working when you drive out of your garage can be frustrating. Even more annoying when you have to drive at night.
For most people, the next step is to take the car to the workshop. This is often the first sensible step if you have a faulty light bulb. First, getting to the light bulb is difficult.
Not only that, but fixing it can seem like a big task. However, it's easier than you think. With a multimeter, you can check the headlight bulbs and replace them if they are faulty. Now, if the problem is with the car, you should take the mechanic to have a look.
In most cases when light bulbs stop working, it is often a problem with the light bulb. This means you can fix it without a trip to the mechanic. This guide describes how to test a headlight bulb with a multimeter. Let's get straight to the details!
Quick Answer: Testing a headlight bulb with a multimeter is an easy method. First remove the light bulb from the car. Second, place the multimeter leads on both sides of the bulb to check for continuity. If there is continuity, a reading on the device will show it. Then check the connector to make sure there are no other problems.
Steps to test a headlight bulb with a multimeter
It is important to note that some vehicles come with a set of spare bulbs. You can find them in the trunk of your car. If your car did not come with a kit, you can buy a new kit from the store.
It is recommended to have at least one kit in the car for easy replacement in case of bulb failure. A set of new bulbs can cost anywhere from eight to one hundred and fifty dollars. The actual cost will depend, among other things, on your vehicle type and output socket.
Now let's proceed directly to checking the car light bulb. Here's how to test an LED headlight bulb with a multimeter. (1)
Step 1: Removing the Light Bulb
Here you will need a digital multimeter. You don't need to purchase an expensive device to get the job done. The first thing to do here is to remove the glass or plastic cover on the vehicle. This is to get to the light bulb. After removing the cover, carefully unscrew the light bulb to remove it from the socket.
Step 2: Setting up the multimeter
Select your multimeter and set it to continuous mode. You can also set it to 200 ohms, depending on your device type. It's easy to check if you've set your multimeter to continuous mode correctly. To do this, connect the probes together and listen to the beep. If it is correctly set to continuous mode, it will generate sound.
The next thing to do is find your base number. You will need to double check the numbers you get with the base number with the actual number you get after checking the car light bulb. This will let you know if your bulbs are working or not.
Step 3: Probe Placement
Then place the black probe in the negative area of the lamp. Place the red probe on the positive pole and press it momentarily. If the bulb is good, you will hear a beep from the multimeter. You won't hear any sound if the lamp switch is broken because there is no continuity.
You can also check if your lamp is good by checking its appearance. If you see black dots on the inside of the bulb, it means the bulb is broken. However, if you don't see any signs of cracking or overload damage, the problem may be more related to internal damage. That's why you need to test it with a digital multimeter.
Step 3: Understanding what you are reading
If you have a faulty light bulb, the DMM will not show any readings, even if the light bulb physically looks good. This is because there is no loop. If the bulb is good, it will show readings close to the baseline you previously had. For example, if the baseline is 02.8, a good lamp should be within the reading range.
It is worth noting that the type of bulb used in your vehicle will also determine the reading. For example, if you are using an incandescent bulb, if it reads above zero, that means the bulb is still working. However, if it reads zero, that means the light bulb needs to be replaced.
If your headlight bulb is fluorescent, a reading of 0.5 to 1.2 ohms means that there is continuity in the bulb and it should work. However, if it reads below the minimum, it means that it is defective and needs to be replaced.
It is worth noting that a successful reading does not mean that the light bulb is working well. So if your light bulb is not working even when the DMM shows it to be in perfect condition, you should visit your local machine shop to have an expert take a look.
Step 4: Checking the Connector
The next step is to check the health of the connector. The first step is to unplug the connector around the back of the bulb from the car. You must be careful when disconnecting the connector not to pull the wire out of the connector. (2)
The connector has two sides. Place the probe on one side of the connector. If you are using a 12VDC base voltage, you can set it to 20VDC on the DMM. Next, go inside the car and turn on the headlight to see the readings.
The reading should be as close to the base voltage as possible. If it is very low, it means that the problem is in the connector. If the connector is good, then the problem is with the lamp or lamp switch. You can replace the light bulb or fix the problem with the switch to solve the problem.
You may be interested to know that you can do this on other bulbs. You can check your household light bulbs that no longer work. The principles are the same, although you may see some differences in the output.
You can also use this method to test Christmas lights, microwaves, and other household items. If there is a break, the multimeter will emit a sound or light signal.
Summing up
With these simple steps, you can check your headlight bulbs and fix any issues with them. If the problem is with the light bulb, you can fix it yourself. All you need to do is buy a new bulb and replace it and your headlight will come back to life.
However, if it's a mechanical issue, such as a switch or connector issue, you may need to visit a mechanic.
Take a look at some of our articles below.
- How to test a halogen light bulb with a multimeter
- How to check Christmas garlands with a multimeter
- Setting the integrity of the multimeter
Recommendations
(1) LED - https://www.lifehack.org/533944/top-8-benefits-using-led-lights
(2) car – https://www.caranddriver.com/shopping-advice/g26100588/car-types/
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