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]
Hi my question is our new van has a 12 pin plug the van has the usual fridge etc but it also has a battery..van is a jayco flamingo 2014 should we keep the 12 pin plug or change it ?
Hi Chris, we would recommend would keeping the 12 pin but bypass the battery charge feed from the 12 pin and run the charge feed through an Anderson Plug instead. This will allow more current pass through and stop any melting of the 12 pin pins.
Hi Briohny, 2 years ago an auto electricain wired my 80 series LC for electric brakes(Primus IQ), as we had bought a Jurgens dual axle caravan. The connector now needs replacing and on taking the cars connector to bits I find that the wires do not match the Narva connectors, I have bought. A 5mm Red & Black wire has been added! The car connector has 1=Y,2=5mm Red, 3=W, 4=G, 5=5mm Black,6=R,7=Brwn.So I replaced them one for one with the new connector.I noticed the blue wire was not used.
My worry is that the caravans connector has the Blue wire on pin 5? However the pin 5 is occupied by the 5mm Black, on the car connector?
I looked under the dash and the wiring to the Primus IQ has been connected up using two 5mm Red and Black cables, as follows. Primus Black (battery 12+) connected to two 5mm Reds, Primus White ground (battery negative)connected to one 5mm Black, Primus Blue (brake) connected to one 5mm Black. The Primus Red is connected to the cold side of the foot brake (G/W).
Your advice would be appreciated, as I do not want to burn anything out. Johno.
Hi John, everything sounds like it is in order. If you are concerned at all, we always recommended taking your vehicle to an Auto Electrician. This is the kind of thing we do all day every day so for peace of mind when you’re on the road, it’s usually the best option.
Hi Briohny.
I have a 7 pin round metal plug on my tow vehicle and caravan. I charge my caravan fridge from the car battery through one of the pins while I’m driving. (I unplug the connectors when we pull up).
I have no Anderson plug.
I am going to get a battery installed in my caravan. Can the car battery charge the caravan battery through one of the pins while I’m driving or do I need to install an Anderson plug for this purpose? Meaning extra cabling will need to be installed through the caravan to the caravan draw-bar and cabling from the car battery through the car to the back of the car?
Regards.
David.
Hi Kevin
Can you tell me if the blue wire on pin 5 of the factory fitted trailer 12 pin connector on my Ford Ranger can be removed completely. At the moment on pin 5 there is the original blue wire and a blue wire from my brake controller. I need to loop pin 5 brake controller wire around to pin 11 for my new caravan, but the pin hole is too small for three wires.
Hi Kevin
Sorry I resent my question please ignore and THANKS very much for your response
Cheers
Hi
I own a Ford XLT Ranger and have a brake controller with its blue wire connected directly to pin 5 of the trailer socket.There is another blue wire connected to this same position, Ford call Services Brake. Can I remove this wire as I need to loop the brake controller wire around to pin11. My new caravan requires pin 5 and 11 for this input.
Hi Terry,
Yes, remove the factory wire in pin 5 and fit a wire direct from the brake controller.
Hi.
What voltage should I be getting at my tow vehicles anderson plug when the engine is running.
Hi Kevin, it depends on the vehicle you have, the size and style of the alternator on the tow vehicle will mean different voltages.
Just bought an old caravan with Britax 12 pin plug. Doesn’t fit car 7 pin fitting. Can’t find a connector to suit in any of the shops, so is it off to an auto electrician?
Caravan has gas/electric frig, gas stove. Has an exterior battery to run a couple of led lights.
Hi Kerry,
We always suggest getting a 12 Pin conversion done on your vehicle, it will be more secure than a connector and is a more universal solution if you ever need to tow anything else.
We have a Britax 7 pin power plug on our caravan. After a 1 half hour trip we parked at the caravan park. The plug would not separate from the vehicle plug also 7 pin, by prying off the plug it was evident that one one of the wires had gotten very hot and blackened the number 2 pin, (reversing signal). This wire was thicker than the others & coloured pink. Can you tell us why this has occurred? We have an Anderson plug also installed. Thank you.
Hi Carol,
If the Fridge feed is drawing through 7 pin it can draw up to 16 amps. We would recommend either fitting 12 pin plugs or use another Anderson plug to power the fridge in your caravan (preferably a different colour so you don’t get the two confused).
I’m glad you shared this helpful information with us. Please keep us up to date like this. This is actually a good and useful piece of information. thank you for sharing.
Thanks Jack, glad you found the post helpful. Be sure to check out some of our other blog posts for more useful tips.