Fit an auxiliary wire to your vehicle to run the caravan refrigerator on 12 volts whilst you are travelling.

In most cases when Hardings install an Electric Brake Controller into a vehicle we will run an auxiliary wire at the same time. This will allow the caravan refrigerator to operate on 12 volts whilst you are driving and the internal lights on the van to work from the car battery. 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 at the socket it matches up to standard wiring in the caravan. In a passenger vehicle Hardings usually run the wire internally, on a four wheel drive it is most common to be run inside the chassis rails.

Why run the caravan on 12 Volts?
Most caravans have a 12 volt lighting circuit which is connected to the 7 pin plug. It is useful to be able to turn on the lights when not connected to mains power. This could be simply to find something in the caravan during night time travelling or to allow a night or two in a national park where no mains power exists. Unless you have a dedicated battery in the caravan lights will not be possible in the caravan without an auxiliary wire in the car.

Also, most caravans are installed with a 3 way refrigerator. The 12 volt option can be used whilst travelling to keep your fridge cold between stops. This will be a great advantage for long distance travelling in warm climates.

Current draw (amperage) requirements of the fridge.
Your 3 way fridge has a 150 watt element fitted which needs a thick heavy duty wire (minimum 6mm gauge) to work efficiently. This wire should be run directly to the car battery via a fuse and not short cut from other power supply points (e.g. the boot light) This single heavy duty wiring option provides effective fridge operation and is the most popular choice.

An even more successful wiring option is to run a 6mm twin wire to the positive and negative terminals of the car battery back to a separate connector between the car and van. This is better because the standard 7 pin connector has a “loss factor” due to terminal size and amperage capacity. The only problem is the requirement for special wiring on the caravan to match up to.

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. Hardings have some switching options to help with this. Here is a summary:

1. Auxiliary Wire, No Switch: When you stop driving you need to either pull the plug out of the back of the car or go into the van and turn the fridge off.
    

2. Auxiliary Wire with Manual Switch: A neat rocker switch with a light on it fitted under the dash to remind you when the auxiliary wire is active. When you stop for a long break simply push the switch on the dash to protect your cars battery.
    

3. Auxiliary Wire with Automatic Switch: The auxiliary wire is turned on and off by the ignition of the car. In some cases this option is difficult due to sophisticated electrics in modern motor vehicles. Talk to Hardings about this.
    

4. Fridge “Motion Sensor” Switch: This product, normally fitted in the caravan in conjunction with a basic auxiliary wire in the car only allows current to flow to the fridge whilst you are driving. This is our preferred option because it provides foolproof battery protection and is independent of the electronics of your motor vehicle.

Does the auxiliary wire charge a battery in the caravan?
No, A battery charging circuit has special requirements. Even heavier cabling (8mm twin) is required through a separate socket (usually an Anderson Plug) but more important is the need for a battery management system in the car to protect the car’s alternator and computer. This is a specialist auto electrical installation beyond the scope of our auxiliary circuits.

See the following table for a summary of Options and pricing.