Confused about what trailer plugs you need? Our simple explanation explains all. Hi, I’m Briohny from Accelerate Auto Electrics & Air Conditioning on the Sunshine Coast. Some of the most common questions we get asked as auto electricians are, what the different types of trailer plugs are, and what each one is used for.

Today we’re gonna take a look at the most common options for trailer plugs, the five pin, seven pin, twelve pin, and also the Anderson plug. They’re called five, seven, and twelve pin plugs because they connect five, seven, or twelve wires on your car to your caravan or trailer.  So, if you turn the indicator on in your car, the first pin connects the signal in the car to the trailer indicator and makes the trailer indicator work. So let’s take a look at each plug.

5 Pin Trailer Plug

First up we have the five pin, which only comes in the round. In Andrew’s twenty years of being an auto electrician on the Sunshine Coast, he hasn’t actually ever seen one of these. They are definitely the least common, but they do connect very basic things. They connect the left-hand indicator, the right-hand indicator, a return to earth, your brake lights, and your taillights, including clearance and sidelights.

7 Pin Trailer Plugs

Next up is the seven pin trailer plug, which comes in flat or round. In the round, you can get a big size, or a small size. Usually the big is used on trucks or heavy machinery. These vehicles have a lot more lights and require more power to be fed through the plug. The seven pin connects all of the things that we mention with the five pin, plus reverse lights, and an electronic brake controller. We prefer using the flat over the round because in our experience, the wiring is more likely to get damaged in the round.

Also, you can plug a seven pin flat into a twelve pin flat, making it more versatile. On the tow vehicle, our preference is to mount a twelve pin flat. If you tow a trailer or caravan that has either a seven pin flat or twelve pin flat, both of these can plug into the twelve pin on your car.

12 Pin Trailer Plugs

Next up, we have the twelve pin plug. You get everything that you connected on the five and seven, plus you now have five extra pins to wire up various accessories. This could include:

  • A fridge ignition feed to power the fridge in your caravan or trailer while you’re driving.
  • A breakaway battery monitor. This allows the voltage of the battery on your breakaway unit to be displayed on the dash of your vehicle.
  • ESC, which is Electronic Stability Control, if your caravan has it.
  • Or a heavy earth return.

Each caravan and trailer manufacturer wires up their plugs differently. We always request a wiring diagram from the caravan or trailer manufacturer to confirm what needs to be wired to what pin.

Anderson Plugs

Lastly, we have the Anderson plugs. The Anderson plug is most commonly used to charge the batteries in your trailer or caravan when you are driving. You can do this via a twelve pin plug, but we don’t recommend it. The power that is fed into the plug to charge the batteries is generally more than a twelve pin plug can handle.

We regularly see melted twelve pin plugs when people charge the batteries via them. You can get the Anderson plugs in grey, red, or blue. Each coloured plug does not physically fit into the other colour, so you use a different colour to ensure that you plug them into the right device.

When it comes to getting your vehicle wired up to tow a trailer or caravan, there are few things we recommend. If you plan to tow a caravan, we usually suggest getting an Anderson plug installed, especially if you want to charge your caravan’s battery from your vehicle. Twelve pin trailer plugs are not designed to hold a charge feed and will usually melt when exposed to that much current.

If you have any other questions about the plugs, your car, caravan, or trailer needs, comment below, or call us at 1300 227 353, or email [email protected]