A trailer wiring connector is what links your car’s electrical system to the trailer, allowing other drivers to see your lights even with the trailer blocking the rear of your car. This is not only a safety measure; it’s also the law. Requirements vary from state to state, so double-check the laws in your area to make sure you’re in compliance. Here’s a rundown on the most common types of trailer wiring connectors and how they work.
Types of Plugs and Sockets
In your house, you plug appliances into wall sockets. With your car, you plug your trailer into a vehicle socket. The shapes of the plugs and sockets vary, with the most common types being flat, round and RV blade.
- Flat: Flat connectors have all the pins lined up in a single row. Generally, you’ll find that flat connectors have a lower number of pins and are used for towing smaller loads, which don’t require as many functions.
- Round and RV Blade: Both of these connectors are round with the pins arranged in a circle. On six-pin connectors and higher, there’s also one in the middle. Though these do sometimes come with smaller pin counts, they most commonly have a higher number of pins and are used for larger loads that require additional functions.
The shape of the outlet and plug are the same for round and RV blade connectors, but the shape of the pins and holes changes. Round plugs have round pins and holes; RV blade plugs have rectangular pins and holes.
Let’s go back to what you have in your house. Household outlets work with two-pronged or three-pronged plugs. With trailers, think pins instead of prongs. So, imagine a four-pin trailer wiring connector as if it’s simply a household plug with four prongs. The most common trailer connectors have four, five, six or seven pins. The more pins in the connector, the greater the number of functions it can handle.
- Four-Pin and Five-Pin: Every connector has one pin that’s a ground, so a four-pin connector controls only three things, a five-pin connector only four things and so on. It’s all about lights with a four-pin connector, which controls the turn signals, brake lights and taillights. Move up to a five-pin trailer wiring connector and you add reverse lights or electric brakes, depending on the plug.
- Six-Pin: Once you get to a six-pin trailer wiring connector, you add a 12-volt connection, which is more about convenience than safety. Rather than controlling the lights, this sixth pin is what’s called a hot lead, and it will let you charge the battery in your trailer. It’s unnecessary if you’re towing something like a boat, but it comes in handy if you’re hauling a small camper trailer.
- Seven-Pin: A seven-pin trailer wiring connector adds even more capacities. It includes the capabilities of the various smaller pin sizes, so you have all the lighting functions, electric brakes and the 12-volt outlet. Again, this isn’t something you need on a smaller trailer, but when you’re towing a camper or an RV, it becomes much more important.
The variety of available trailer wiring connectors ensures that you have the right features no matter what kind of load you haul. Tow safely and legally with one of these types.
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Nicole Wakelin covers the automotive industry as a freelance journalist for a variety of outlets. Her work includes news pieces, podcasts, radio, written reviews, and video reviews. She can be found in The Boston Globe, CarGurus, BestRide, US News and World Report, and AAA along with lifestyle blogs like Be Car Chic, The Other PTA, and She Buys Cars. She is active on social media with a large following on both Twitter and Instagram and currently serves as Vice President of the New England Motor Press Association.