Understanding the Differences Between 3157 and 3156 Bulbs

[LASFIT]

The 3157 and 3156 are two widely used bulbs for turn signals, brake lights, and taillights. Have you ever learned about these two types of lights when you were picking out LED turn signals for your vehicle? Is there still some confusion about the difference between these two? Are you not sure how to pick the right bulb? This article will introduce you to 3157 and 3156 and hopefully help you out!

What's The Difference Between 3157 And 3156?
The main difference between 3156 and 3157 bulbs lies in the number of filaments. The 3156 bulb has only one filament, while the 3157 bulb has two filaments.

To determine whether it is LED 3157 or LED 3156, the main difference lies in the wiring. The 3156 bulb has only one wire, while the 3157 bulb has two wires.

Installation Position
As for the installation position, due to the dual filaments of the LED 3157 bulb, it has both high and low brightness, making it a dual-function bulb. When used as a front turn signal, the 3157 bulb can simultaneously function as a turn signal and daytime running light (DRL). When you activate the front turn signal, the high brightness of the bulb serves as the turn signal. In contrast, low brightness is usually used for DRL or parking lights. Additionally, the 3157 bulbs can also be used as side marker lights on some trucks.
When installed in the rear lights, the 3157 bulb is typically used as a tail light and brake light.
On the other hand, the LED 3156 bulb has only one filament, making it a single-function bulb. It has only one brightness level and cannot switch between high and low brightness like the 3157 bulb. It cannot be used simultaneously as a turn signal and DRL.
Due to its attributes, the 3156 bulb is primarily used for front or rear turn signals, reverse lights, and parking lights.

Are 3157 And 3156 Interchangeable?
When replacing or upgrading the lighting system, ensuring compatibility between the existing socket, wiring, and bulb is crucial.
The base of the 3157 and 3156 bulbs is the same, so the 3157 bulb can be installed in the base of a 3156 bulb, and vice versa. But will they work?
When a 3157 bulb is installed in a 3156 socket, it can still illuminate. One of the two filaments in the 3157 bulb will receive power and light up, allowing it to function similarly to a single-filament 3156 bulb.
On the other hand, if a 3156 bulb is installed in a 3157 socket, it will only produce a fixed level of brightness. The reason is the 3156 bulb is intended for single-filament operation, whereas the 3157 socket is designed for dual-filament bulbs. The different wiring of the two prevents the 3156 bulb from functioning in the same manner as the 3157 bulb within a socket specifically designed for dual-filament bulbs.

How To Pick The Correct LED Bulb?
How do you pick the correct LED bulb model? It depends on the size of your factory halogen bulbs. Here are some tips to assist you in choosing the appropriate LED bulb.
1. Review the user manual
You can consult your vehicle's user manual, which typically provides details about the bulb size of the factory halogen bulbs. Once you have determined the bulb size, you can purchase the corresponding LED bulb based on the information in the manual.
2. Inspect the factory halogen lights
You can remove the factory halogen bulb that requires replacement. Usually, the halogen bulb socket will show the corresponding model number. By identifying the model number, you can purchase an LED light with the same model to ensure compatibility.
However, this method is a bit more cumbersome, some vehicles are not convenient to take out the halogen bulb. additionally, individuals with limited experience in bulb modification might be hesitant to undertake this task, fearing potential damage.
3. Search on the Lasfit website
Another useful resource is the Lasfit website, where you can search for the correct LED bulb model specific to your vehicle's make, model, and year. Our website provides detailed categorization, making it easier for you to locate the appropriate LED bulb. Here is the link for you: LASFIT

Conclusion
The difference between 3157 and 3156 is mainly in the number of filaments.
When choosing between LED 3157 and LED 3156 bulbs, it depends on the factory bulb size of your vehicle.
When a 3157 LED bulb is installed in a 3156 socket, the light will function normally. However, if a 3156 LED bulb is installed in a 3157 socket, only one function will work as the 3156 bulb is a single filament bulb.
Lasfit's upgraded T3 series only offers one model, T3-3157, which is compatible with both 3156 and 3157 bulbs. So, whether your vehicle's bulb size is 3156 or 3157 bulbs, you can purchase our T3-3157. However, please pay attention to the color choice - whether you need red or amber.
Have you ever installed LED 3156 or 3157 for your turn signals? Feel free to share your experience with us in the comments!

 

[Jim Oaks]

@LASFIT Here's a topic for you:

I've updated the halogen headlights in my vehicles to LED.

The problem people could have is trying to figure out how bright they're going to be. It's easy understanding the output of a 50-watt halogen bulb vs a 100-watt halogen bulb. But with LED, some lights use less watts but put out as much if not more light than the same watt halogen bulb. Plus, with LED you'll see a lot of reference to lumens. If you're not careful, your lights could be blinding to oncoming traffic.

 

[Curious Hound]

@LASFIT Here's a topic for you:

I've updated the halogen headlights in my vehicles to LED.

The problem people could have is trying to figure out how bright they're going to be. It's easy understanding the output of a 50-watt halogen bulb vs a 100-watt halogen bulb. But with LED, some lights use less watts but put out as much if not more light than the same watt halogen bulb. Plus, with LED you'll see a lot of reference to lumens. If you're not careful, your lights could be blinding to oncoming traffic.

Absolutely. There are at least 2 factors to consider there. One is that many people still do not understand the term "lumens" which is a measurement of the light output. That is the actual rating for brightness.

Secondly, people perceive different light colors as brighter or dimmer. It's not true. But it's a common perception issue. A light with X number if lumens output at a 4500k color rendering will appear yellower and warmer than a light of the same brightness (same number of lumens output) at a 6000k color rendering that is much whiter. This will probably always be an educational issue no matter how well the products are labeled.

Then there is the issue with cheaper lights not being designed properly. So the redlector/lamp positioning does not focus the beam properly and provide cutoff at the right level to prevent blinding oncoming traffic.

Headlights are much more complicated than people realize.

 

[LASFIT]

@LASFIT Here's a topic for you:

I've updated the halogen headlights in my vehicles to LED.

The problem people could have is trying to figure out how bright they're going to be. It's easy understanding the output of a 50-watt halogen bulb vs a 100-watt halogen bulb. But with LED, some lights use less watts but put out as much if not more light than the same watt halogen bulb. Plus, with LED you'll see a lot of reference to lumens. If you're not careful, your lights could be blinding to oncoming traffic.

Thank you for your suggestion. We will use threads/blog/video formats to explain to everyone some factors related to LED brightness, helping everyone choose the LED lights they need.

 

[LASFIT]

Absolutely. There are at least 2 factors to consider there. One is that many people still do not understand the term "lumens" which is a measurement of the light output. That is the actual rating for brightness.

Secondly, people perceive different light colors as brighter or dimmer. It's not true. But it's a common perception issue. A light with X number if lumens output at a 4500k color rendering will appear yellower and warmer than a light of the same brightness (same number of lumens output) at a 6000k color rendering that is much whiter. This will probably always be an educational issue no matter how well the products are labeled.

Then there is the issue with cheaper lights not being designed properly. So the redlector/lamp positioning does not focus the beam properly and provide cutoff at the right level to prevent blinding oncoming traffic.

Headlights are much more complicated than people realize.

Thank you for your suggestion. You are absolutely right. Color temperature affects color. 4500K~5000K is a warm color with good penetration. 6000K is crystal white lighting, more conducive to illumination. Brightness is mainly related to wattage, lumens, and lux. We will provide some thread information later to help everyone better understand LED bulbs and then choose the LED bulbs they need.

 

[sgtsandman]

Thank you for your suggestion. You are absolutely right. Color temperature affects color. 4500K~5000K is a warm color with good penetration. 6000K is crystal white lighting, more conducive to illumination. Brightness is mainly related to wattage, lumens, and lux. We will provide some thread information later to help everyone better understand LED bulbs and then choose the LED bulbs they need.

If you could link the three in some way, that would be great for those of us who are used to watts as a measure of brightness.

Lumens is informational too but sometimes makes it difficult to figure out what an existing electrical circuit can support or what wire gauge and fuses will be needed to support building a custom electrical circuit.

Especially if all the needed information isn't listed on the web site when looking to order lights.

 

[Curious Hound]

If you could link the three in some way, that would be great for those of us who are used to watts as a measure of brightness.

Lumens is informational too but sometimes makes it difficult to figure out what an existing electrical circuit can support or what wire gauge and fuses will be needed to support building a custom electrical circuit.

Especially if all the needed information isn't listed on the web site when looking to order lights.

You really need both numbers when evaluating the lamps/LEDs. Watts are not directly couple to lumens because different technologies have different efficiencies. 55watt old style incandescent vs 55watt quartz halogen vs 55watt HID vs 55watt LED will all have different brightnesses. Each technology has a different efficiency when converting electricity into light and heat.

 

[RobbieD]

You really need both numbers when evaluating the lamps/LEDs.

I agree that both specifications are needed.

Lumens let me compare how bright the light is versus others.
Wattage lets me compare the current draw between light bulbs.

For example, on my older trucks I would like to change the interior light bulbs from the original incandescent to LED to reduce battery drain while the doors are open.
A wattage specification would let me calculate how much the current draw will be, as towards the goal of reducing the battery drain, and lumens specification would let me compare what to expect as to how bright the lighting would be.

LASFIT, it looks like you do offer a good product that you are proud of, and your trying to offer better technical information about lighting, and the electrical and installation issues related to lighting, in my opinion greatly enhances your product and your company. It helps separate you from your competitors.

Good luck!

 

[LASFIT]

I agree that both specifications are needed.

Lumens let me compare how bright the light is versus others.
Wattage lets me compare the current draw between light bulbs.

For example, on my older trucks I would like to change the interior light bulbs from the original incandescent to LED to reduce battery drain while the doors are open.
A wattage specification would let me calculate how much the current draw will be, as towards the goal of reducing the battery drain, and lumens specification would let me compare what to expect as to how bright the lighting would be.

LASFIT, it looks like you do offer a good product that you are proud of, and your trying to offer better technical information about lighting, and the electrical and installation issues related to lighting, in my opinion greatly enhances your product and your company. It helps separate you from your competitors.

Good luck!

Thank you very much for your recognition! We will continue to work hard to produce better products and content, providing excellent service to car owners in need! Currently on the market, good quality LED bulbs, compared to OEM halogen bulbs, are generally low power, low consumption, high lumen output, and high brightness. Because LED bulb technology is relatively mature, it is recommended that everyone choose high-quality LED bulbs when making a purchase.

 

[LASFIT]

You really need both numbers when evaluating the lamps/LEDs. Watts are not directly couple to lumens because different technologies have different efficiencies. 55watt old style incandescent vs 55watt quartz halogen vs 55watt HID vs 55watt LED will all have different brightnesses. Each technology has a different efficiency when converting electricity into light and heat.

Yes, you are absolutely right. Thank you very much for your comment!

 

[LASFIT]

If you could link the three in some way, that would be great for those of us who are used to watts as a measure of brightness.

Lumens is informational too but sometimes makes it difficult to figure out what an existing electrical circuit can support or what wire gauge and fuses will be needed to support building a custom electrical circuit.

Especially if all the needed information isn't listed on the web site when looking to order lights.

Okay, we will take note of this point in future articles and strive to provide clearer information for everyone. We will also add this information to the website details.