A guide to trailer adaptors
Tom Vondrasek | 15th Nov 2023 | 3 minutes to read
Trailer adaptors might seem like complex devices, but they’re actually relatively simple. They connect your vehicle’s electrics to your trailer’s electrics, and as long as you have the correct one, it is simply a matter of plugging one end into your trailer's connector and the other end into your car’s connector.
Not having the correct adaptor or not having an adaptor at all is where the fun starts.
In this guide we’ll take a look at some of the key features of a trailer adaptor and how to select the right one:
Why Trailer Adaptors Are Important
Trailer adaptors are a necessary requirement when driving with a trailer as whatever trailer you tow needs to mimic the lights on the rear of your vehicle. This is obviously important, as you now have a trailer in the way and it needs to let the following drivers know if you are braking, turning, reversing, or so they can see you in the dark. A lot of trailers now use electric brakes, so this is another important feature you need connected.
Wiring a Trailer Adaptor
There is a connector on the rear of your car, normally located near the towbar. The trailer also has a connector near the end of the A frame that hooks onto the towbar. The trailer adaptor is designed to connect these 2 together as they are not always identical in shape or in the number of sockets or pins that they have.
Below is a simplified wiring diagram showing 2 different connectors on a vehicle and trailer, the correct adaptor and standard pin outs and trailer wiring. The example is a tandem car trailer though a boat, caravan, or simple box trailer will all be similar when it comes to wiring.
An easy way to keep track of which adaptor you need is to use your smartphone. You can take a picture of the connector on your car and a picture of the trailer connector. The only thing you need to make sure is that you get a picture of the sockets or pins on the connector. A lot of connectors have a simple spring-loaded dust cover cap on them that you may need to hold or wedge open to get your photo.
Below are two different styles of trailer plugs that require an adaptor to connect:
Trailer plug on a car.
Trailer plug on a caravan.
Once you have the pictures, it’s just a case of looking it up online or heading into your local Repco store to get what you require.
Checking Your Trailer Adaptor
Trailer adaptor packaging is very good these days and spells out which end goes to the vehicle and also the trailer. It lets you know the number of pins and the connector type. The back of it contains a standard wiring diagram. This is very handy when it comes to finding fault with your trailer parts.
When fitting a new trailer adaptor, it is always good the check that all your lights are working correctly. If you have electric brakes these definitely need a slow speed test to make sure they are working.
The other vital thing you need to check is that the trailer adaptor or wiring is not going to hit the road when going over a bump. You also don’t want it too tight so that when turning it could pull out or partially disconnect. A few well positioned cable ties work well in this instance. Keep them loose enough for the cabling to move when turning and keep the cabling from hitting the road or getting jammed in other parts of the trailer.
