Fit an Auxiliary Wire for your Caravan Refrigerator

In most cases when Swift Caravan Services install an electric brake controller into a vehicle we will recommend an auxiliary wire at the same time. If you have a three way refrigerator in your caravan, this will allow the fridge to operate on 12 volts from the vehicle alternator whilst you are travelling, and on vans without a battery system, the internal lights in the van can run from the car battery too. These functions are built into your caravan as standard features and are well worth using! When deciding whether and how to use the auxiliary circuit in your van consider the following issues and questions.

What is an Auxiliary Wire?

It is a dedicated wire run from the car’s battery via circuit protection to the rear socket of the car. Usually connected to pin 2 in a 7 pin plug, or pin 8 or 9 in a 12 pin plug, it matches up to standard wiring in the caravan. In a passenger vehicle, Swift Caravan Services usually run the wire internally, on a four wheel drive it is most common to be run inside the chassis rails. Some caravans with larger fridges will run the fridge wires through a separate Anderson plug.

Current draw (amperage) requirements of the frigde

Your 3 way fridge may have up to a 250 watt element fitted which needs a thick heavy duty wire (minimum 6mm gauge, preferably 8mm) to work efficiently. Some fridges can draw well over 10 amps, constant. The auxiliary wire should be run directly to the car battery via a fuse or circuit breaker and not short cut from other power supply points (e.g. the boot light).

How to prevent a flat battery in your car

If you stop for lunch during your drive you need to ensure that the caravan fridge is not continuing to draw on the car battery. Otherwise it won’t be too long before your car may not start.

Auxiliary Wire with Ignition Switch: The auxiliary wire is turned on and off by an ignition activated relay in the car. This is our most common option these days as most vans are equipped with batteries to run the rest of the 12v equipment, except the refrigerator. The relays we use are designed to complement the complex electrical systems in modern vehicles.

Does the auxiliary wire charge a battery in your caravan?

No, a three way fridge should have its own dedicated circuit, and a battery charging circuit has special requirements. Even heavier cabling (8mm twin minimum) is required, either through an Anderson Plug, or a 12 pin plug.

AES (Auto Energy Select)

If you have an AES fridge, you will also need an exciter wire in your trailer plug, which is ignition operated. This tells the caravan fridge when 12volt power is available, and when to look for an alternative power source.

Wiring Diagram

Caravan manufacturers don’t all wire their vans the same way. For instance, some common locations for a fridge wire are pin 2, pin 8, pin 9, pin 11, or it could be through an Anderson plug. If you can get a wiring diagram from your caravan manufacturer before we wire your car, we can ensure every circuit will be in the right place to match your caravan first time.