Trailer Connector Types: How to Tell What You Have and What to Order

john78372
7 days ago
5 min read

You're ordering a light, the form asks whether you want a 4-pin or a 7-blade connector, and you realise you have no idea which one is bolted to the back of your car.

Fair. The naming in this corner of the world is genuinely a mess — the same connector goes by four different names depending on who's selling it. So here's the whole picture: how to tell what you've got, what the other types are for, and which words actually mean different things versus which are the same thing wearing a different hat.

First, go look

This takes thirty seconds and beats any amount of reading.

Go to the back of your vehicle and look near the hitch receiver, or just inside the bumper. You're looking for a socket, sometimes behind a little rubber cap, sometimes tucked up out of sight on a short pigtail.

Trailer wiring sockets on a vehicle bumper with protective covers closed

This is what you'll find first — both connections, covers closed.

Count the holes.

Four holes in a flat plastic rectangle — that's a 4-pin flat. Most cars, crossovers and SUVs with a hitch.

Seven holes in a round housing about the size of a shot glass — that's a 7-blade. Most trucks, and most vehicles that came with a factory tow package.

Something else — five, six, or seven holes that don't match either description. Keep reading, and see the section on the rest of them.

If you find nothing at all, your hitch was likely fitted without wiring. That's a separate job and a normal one.

The two we build for

Kody lights come with a 4-pin or a 7-blade. Both work with every light we make, so this isn't a question of one being better.

Four-pin flat trailer connector on a vehicle bumper, cover held open

A 4-pin flat. Four contacts in a flat plastic rectangle.

4-pin flat. Four contacts: ground, running lights, left turn and brake, right turn and brake. That's everything a bike rack light actually needs, and it's why it's the default.

Seven-blade trailer connector on a vehicle bumper, cover held open

A 7-blade. Round housing, flat blade contacts inside — which is where the name comes from.

7-blade. Seven contacts — the four above, plus electric trailer brakes, 12-volt auxiliary power and reverse.

Here's the part worth knowing: we only use five of those seven. The same four the 4-pin carries, plus reverse. Electric trailer brakes and 12-volt auxiliary we leave alone, because a bike rack has no use for either. Picking the 7-blade doesn't mean you're wiring in trailer brakes.

So there are four real reasons to choose it:

Your vehicle already has one — you plug straight in, with no adapter hanging off the back.

You get a heavier cable and jacket.

You get the plate light connection built in, which is the one that saves you trouble later.

And reverse lights become available on the Medium and Large.

The honest advice: match what's on your vehicle. If it's a 4-pin, order the 4-pin — you're not missing anything your lights need. If it's a 7-blade, order the 7-blade and take the sturdier cable and the plate-ready connection while you're there.

The rest of them

You probably won't need these, but this is where the confusion comes from.

5-way. A 4-way plus one extra circuit, usually reverse lockout for trailers with surge or hydraulic brakes. Boat trailers, mostly — the lockout stops the trailer brakes grabbing when you back down a ramp.

Good news if this is you: a 4-pin plugs straight into a 5-way. The fifth contact just goes unused. Order the 4-pin and carry on.

6-way. Adds electric brakes and 12-volt auxiliary power. Round ones turn up on horse trailers, square ones on older campers.

7-way with round pins. Seven contacts like the blade version, but round pins instead of flat blades. Not interchangeable with a 7-blade despite the matching count.

In practice you're unlikely to meet either of the last two on a passenger vehicle. In all the kits we've shipped, I've never had a customer turn out to have one. If you do, send me a photo and we'll work it out.

The terminology, decoded

This is the part nobody explains.

Pin, pole and way all mean the same thing. A 4-pin, a 4-way and a 4-pole are one connector. Three words, one object, no difference. Retailers just picked different house styles and never reconciled them.

Flat and round describe the housing, not the pins. A "4-pin flat" is a flat slab of plastic. A 7-blade lives in a round housing — but the contacts inside are flat blades, which is where the name comes from. So a round-looking connector with flat pins is entirely normal. You'll see it sold as a "7-way round", which is why people assume the pins are round. They usually aren't.

We call it a 7-blade connector and leave the shape out of it.

7-way, 7-blade and 7-pin RV are the same thing. The RV part is just where the standard came from.

SAE 2-pin is a different animal — a small two-contact plug used for accessories rather than for connecting to your vehicle. It's what our plate lights plug into, branching off the main cable rather than off your bumper.

A pigtail is the short cable and socket hanging off the vehicle. An adapter converts one type to another. A converter is a box that changes how the signals themselves work, which is not the same thing, and the difference matters in the next section.

When your connector isn't the whole story

Having the right connector doesn't guarantee everything works, and this catches people out.

Newer vehicles run trailer lighting through more sophisticated electronics than they used to. LED lights draw very little current, and some vehicles read that low draw as a fault — you get rapid flashing, a warning on the dash, or the lights simply not coming on. Some vehicles also register the rack as a trailer and change how the lane-departure and blind-spot systems behave.

Full-size Fords from 2021 on are the toughest case. Our LED trailer light compatibility page covers what's going on and what to do about it.

Short version: if you drive a newer Ford or a Tesla, read that page before you order.

What to pick

Match your vehicle. That's the whole decision.

4-pin on the bumper, order the 4-pin. 5-way, also order the 4-pin — it plugs right in. 7-blade on the bumper, order the 7-blade and take the plate light connection while you're there.

Anything else, or nothing at all — get in touch and send a photo of the socket. I answer these myself, and it's a faster conversation than guessing.

Ready to order? The buyer's guide to light sizes covers the other decision, and the connector guide has the short version of this page next to the order options.