How to Replace Bulb Sealed Trailer Light (The Right Way)

That moment when you realize one of your bulb sealed trailer lights is out and needs replacing. We’ll take a deep dive into how you can replace that bulb sealed light the right way, without unnecessary hiccups or fumbling around.

How to Replace Bulb Sealed Trailer Light

Can I Fix the Bulb Sealed Light Without Replacing It

Usually, the answer is no. Since the parts are sealed inside, it’s tough to get to them to make repairs. You might be able to fix a small problem temporarily, but for most issues, it’s smarter to replace the whole light. Think of it like a puzzle that’s glued together, you can’t take it apart to fix just one piece, so it’s often easier to start fresh with a new one.

Finding a Match for the Existing Set of Lights

When embarking on the journey of replacing a bulb sealed trailer light, finding a match for the existing set of lights isn’t just a casual step, it’s a must. The harmonious combination of the socket, size, and even brand (though that’s optional) plays an instrumental role in ensuring the light functions flawlessly and integrates seamlessly with your trailer. Here’s a close look at these key components.

Matching the Socket

The socket is like a puzzle piece that must fit snugly into its corresponding part. It’s more than just a simple connection, it’s an intricate alignment that demands compatibility. Choosing the right socket ensures that the electric current flows smoothly, and the light functions as intended. The wrong socket could lead to electrical mismatches, resulting in erratic lighting or even worse, a short circuit. So, while this might seem like a small detail, it’s actually a cornerstone in the larger edifice of your trailer’s lighting system.

Matching Unit Size

Now, let’s talk size. Size in the context of trailer lights is not merely a matter of aesthetics but functionality. A mismatched size might not just look odd, it could lead to improper fitting, causing potential leakage or exposure to external elements. Selecting the correct size ensures that the new light aligns perfectly with the existing setup, eliminating unnecessary gaps or overlaps. 

Matching the Same Brand (optional)

Brand selection might be significant for those who have specific preferences or have had unique experiences with certain manufacturers. Sticking with a brand that’s familiar might provide peace of mind, especially if it has proven reliability or offers warranties that align with your expectations. 

On the other hand, exploring different brands might open doors to innovative features or cost-effective solutions. The choice of brand is more flexible, like selecting a wine to go with dinner, you can choose what you know or try something new, depending on your taste and comfort level.

How to Replace Trailer Light Unit

If you’ve noticed a dull glow or, even worse, complete darkness emanating from your trailer’s rear, then this handy guide is tailored just for you. Replacing the light unit might sound like a task for professionals, but with a bit of courage and a dash of finesse, it’s something that can be done in your driveway. From taking off the old light to fitting in the new one, let’s walk through the steps together, seasoned with some pro tips to get the most out of the process.

Step 1: Take off the Light

Removing the light is the first hurdle. But don’t worry, with the right tools and a modicum of mechanical inclination, you’ll find it’s as simple as unscrewing a lid from a jar. Carefully detach the light from its mounting point, making sure not to damage the surrounding area.

Step 2: Unplug It From the Trailer

Here’s where attention to detail matters. The wires that keep the light shining bright must be disconnected with caution. Finding the right connection point and gently unplugging it will save you from a tangle of wires and potential electrical mishaps.

Step 3: Plug in the New Unit

The anticipation builds as you bring out the new unit. Matching the wires, color to color is a task that requires both precision and a steady hand. It’s like rethreading a necklace, patience pays off. Once connected, you’re one step away from lighting up the road once again.

Step 4: Fit the New Unit

Now comes the satisfying part. Fitting the new unit into place feels like the final piece of a puzzle snapping into position. Tighten it securely, making sure it’s aligned with the trailer’s design, and you’ll have a bright and shiny new light ready to guide your way.

Pro Tips: Recycle the Old Unit

Waste not, want not. Your old unit, even though dimmed, might still have some life left. Recycling it could give it a new purpose.

Replacing the Trailer’s Wiring Harness if It Is Damaged

When it comes to trailer lights, sometimes the issue isn’t the bulb-sealed light itself but the wiring harness that connects it all. Think of the wiring harness as the nervous system of your trailer’s lighting. If it’s damaged, replace it. 

Crossover Wiring Harnesses

Crossover wiring harnesses play a crucial role in ensuring that signals and power are transferred accurately across the trailer’s lighting system. When these are damaged, the coordination can be compromised, causing a myriad of lighting issues.

To replace a crossover wiring harness, you’ll need to identify the specific type that corresponds to your trailer’s make and model. Carefully remove the old, damaged harness, paying close attention to the connection points. Once removed, install the new crossover harness, making sure all connections are secure and aligned correctly.

Split Y Wiring Harnesses

The Split Y Wiring Harnesses can be considered a special subset within the wiring universe. They’re designed to divide the electrical current in a specific way, often used in trailers with more complex lighting systems.

Replacing a Split Y Wiring Harness requires meticulous attention to detail. You’ll need to purchase the correct Split Y harness for your particular trailer, then methodically disconnect and remove the damaged piece. When installing the new one, follow the exact path of the original to ensure proper functioning. 

Wiring Color-Codes and Plug Adapters

Wiring color codes and plug adapters are like the language and grammar of your trailer’s electrical system. Understanding the color codes is essential for replacing the wiring harness properly.

Each color represents a different function within the system. For example, the white wire typically grounds the circuit, while the brown one often controls the tail lights. Plug adapters, on the other hand, are the connective tissue that binds different parts of the wiring system.

Frequently Asked Questions

How Long Do Bulb Sealed Lights Last?

Bulb sealed lights generally last between 5,000 to 10,000 hours, depending on the usage, quality, and environmental conditions. Their sealed nature protects them from external factors, but over time, like all bulbs, they’ll reach the end of their illuminative lifecycle.

Can I replace bulb lights with LED lights?

Yes, you can replace bulb lights with LED lights. However, it’s not just a matter of unplugging one and plugging in the other. You’ll need to ensure compatibility with your existing system.

Should I Match the Volt While Replacing It?

Absolutely, matching the voltage is critical when replacing bulb sealed lights. Voltage incompatibility can lead to malfunctions, decreased efficiency, or even damage to the light or your trailer’s electrical system.

What Can Cause the Lights to Be Damaged?

Several factors can cause bulb sealed lights to be damaged. External elements such as road debris, moisture infiltration, and exposure to harsh weather conditions are common culprits. Internal issues such as faulty wiring, overvoltage, or manufacturing defects can also play a role.

Are Trailer Lights 12V or 24V?

Most standard trailers utilize a 12V system for their lighting, suitable for the majority of consumer applications. However, some heavy-duty or specialized trailers might operate on a 24V system. Knowing your specific trailer’s voltage requirements is vital when replacing or servicing the lights.

What Size Is Trailer Wiring?

Trailer wiring typically falls within the 16 to 20 gauge range, although this can vary based on the specific trailer and its intended use. Matching the wiring size is essential to maintain proper electrical flow and safety standards.

What Is the Standard Trailer Wiring?

Standard trailer wiring consists of a color-coded system with different wires responsible for specific functions such as brake lights, turn signals, and ground. Commonly used colors include white for the ground, brown for tail lights, yellow for the left turn, and green for the right turn.

How Do I Test Trailer Wiring?

Testing trailer wiring is typically done using a circuit tester or a multimeter. These tools allow you to identify connectivity and verify that each wire is performing its intended function. Carefully follow the manufacturer’s instructions and safety guidelines during this process.

What Wire Is Used for Trailer Lights?

Multi-strand copper wire is often used for trailer lights. Its flexibility, high conductivity, and resistance to corrosion make it a robust choice for trailers on the road.

How Thick Is 20 Gauge Wire in MM?

A 20-gauge wire translates to a thickness of approximately 0.8mm. This measurement can be vital to know when working with specific connections or fittings, as compatibility in size ensures a proper and secure connection.


Replacing a bulb sealed trailer light isn’t as scary as it seems. It’s a journey filled with matching, connecting, and fitting much like a puzzle for grown-ups. Now go forth and replace that light, making the roads a little brighter and your trailer a lot happier.

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