Towing a Caravan Out of Adelaide: Electrics for Long Trips

This guide is for Adelaide caravanners and camper trailer owners heading north to the Flinders Ranges, across to the Yorke and Eyre peninsulas, or further into the outback. It covers the electrical side of towing: the trailer brake rules, brake controllers, plugs, keeping the van battery charged on long runs, and the checks worth doing before you leave town.

How can we help?

Need it fixed?

Get a quote from a local Towing a Caravan Out of Adelaide: Electrics for Long Trips auto electrician, for anything from a flat battery to a full fit-out.

Get a quote

Buying parts?

Quality auto electrical parts from Ozautoelectrics, an established Australian supplier since 2010, dispatched through a nationwide network. For retail and trade buyers.

Shop parts

Doing it yourself?

Free step-by-step guides written for South Australia conditions, with the parts you’ll need listed for each job.

Browse DIY guides

Auto electrician in Towing a Caravan Out of Adelaide: Electrics for Long Trips?

Are you an auto electrical business? List your business on this site.

List your business on this site

Long, hot runs are what test a van's electrics

Most big trips out of Adelaide start the same way: north on Port Wakefield Road, then on towards Port Augusta at the top of Spencer Gulf. From there, the Flinders Ranges are to the north-east, the Eyre Peninsula is to the west, and the Stuart Highway heads into the outback. The Yorke Peninsula turns off earlier, at Port Wakefield. If you live in the southern or western suburbs, the Northern Connector gets you from the Port River Expressway and South Road to the Northern Expressway without crossing the northern suburbs on local roads.

These are not steep mountain trips like those out of some other capitals. The challenge is distance and heat. You may tow for hours at highway speed in 35°C or more, then crawl over corrugated gravel to a campsite. Every plug, joint and earth gets shaken and heated for days at a time. Small faults that wouldn't matter on a weekend trip to the Barossa can turn into lost brakes or a flat van battery a long way from help.

The trailer brake rules, stated carefully

Trailer brake requirements come from the national Australian Design Rule for trailer brake systems, ADR 38. The current version, ADR 38/05, sets the requirements by Gross Trailer Mass (GTM), the load carried by the trailer's axles. South Australia applies these national standards. Here is a plain-English summary, but always check your van's compliance plate and the current rules with the SA Department for Infrastructure and Transport before relying on it:

• Up to 750 kg GTM: ADR 38 doesn't require brakes, but any brakes fitted must work properly.
• Over 750 kg and up to 2,000 kg: the trailer needs brakes, and overrun (override) brakes are allowed.
• Over 2,000 kg and up to 4,500 kg: brakes must work on all wheels, and the braking force must be controllable from the tow vehicle, so overrun brakes alone are not enough. In practice, that means electric or electric-over-hydraulic brakes with a controller in the car.
• Over 2,000 kg: an emergency (breakaway) system must apply the brakes automatically if the trailer comes off, and keep them on for at least 15 minutes.

Brake controllers and long distances

Most Australian caravans have electric drum brakes run by a controller in the tow vehicle. On a long run, the controller is working every time you slow down, so its wiring has to be solid. A controller fed through thin cable or a poor earth will give weak, inconsistent braking, and that problem gets worse as the joints heat up.

Set the controller's gain with the van loaded for the trip, not empty in the driveway. A van packed for three weeks on the Eyre Peninsula brakes very differently from one packed for a weekend. If you change the load part-way through the trip, recheck the setting. Our guide on installing an electric brake controller covers wiring and setup.

Plugs that survive dust and corrugations

The plug between car and van is the most exposed connection on the whole rig. On gravel roads, dust gets into the pins and sockets, and the plug can rattle loose if the lead is too short or too long. A partly seated plug can drop the brake circuit or the charging circuit without any warning on the dash.

Whether you use a 7-pin flat plug, a 12-pin plug or a 7-pin plus a separate Anderson plug for charging, fit dust caps and use them every time you unhitch. Check the pins for heat marks or green corrosion before each trip. Our comparison of 7-pin vs 12-pin trailer plugs explains what each one carries.

Keeping the van battery charged on the road

On a long run north, you might expect the car to fully charge the van battery while you drive. Often it doesn't. The cable from the car's alternator to the van is long, so voltage is lost along the way. Many newer tow vehicles have smart alternators that lower their output once the car's own battery is full. Heat adds another problem, because battery chargers and some battery types reduce their charge rate when they get hot.

A DC-DC charger with properly sized cable usually fixes the charging side. Mount it somewhere with airflow, not in a sealed, sun-baked compartment, so it doesn't overheat and cut back its output. If you plan to free camp in the Flinders Ranges for several days, pair it with solar. See why a caravan battery may not charge while towing and how much solar you need.

Breakaway batteries in the heat

A breakaway system relies on a small battery on the van, and heat shortens that battery's life just like it does a car battery's. A breakaway battery that tested fine in winter may not hold its charge after a summer parked in the sun. If the system can't apply the brakes when you need it, it isn't doing its job.

Test it before every trip, and check that it's being charged from the car through the trailer plug while you drive, if your system is designed that way. Clip the lanyard to a solid point on the tow vehicle, separate from the safety chains.

Checks before you leave Adelaide

Do these a few days before departure, so there's time to fix anything you find:

• All van lights: tail, brake, both indicators, clearance and side marker lights, and the number plate light.
• Brakes: at walking pace, use the controller's manual lever and feel the van pull up evenly.
• Breakaway: test button or indicator, lanyard in place.
• Charging: engine running, battery monitor showing charge going into the van.
• Plug and lead: fully seated, dust cap working, lead not dragging or stretched on full lock.
• Spares: a few fuses of each rating, a spare globe or two, and some crimp connectors and tape.

Getting work done before the trip

If you need a controller, plug or DC-DC charger fitted, book it well ahead of your departure, then do a short test run with the van loaded. Auto electricians across the Northern Suburbs, the Southern Suburbs and around Port Adelaide do this kind of caravan work regularly.

Parts for this job

Order quality parts online from Ozautoelectrics, dispatched Australia-wide.

Get it done: get a quoteDo it yourself: shop electric brake controllers

Get it done: get a quoteDo it yourself: shop DC-DC chargers

Get it done: get a quoteDo it yourself: shop breakaway kits

Get it done: get a quoteDo it yourself: shop trailer plugs

Questions Adelaide drivers ask

Does my caravan need electric brakes in South Australia?

It depends on the van's Gross Trailer Mass. Under ADR 38, trailers over 750 kg need brakes, and overrun brakes are allowed up to 2,000 kg. Above 2,000 kg, the brakes must work on all wheels and be controllable from the tow vehicle, which in practice means electric brakes and a controller, plus a breakaway system. Check your compliance plate and the current rules with the SA Department for Infrastructure and Transport.

How long must a breakaway system hold the brakes on?

ADR 38/05 requires the brakes to stay applied for at least 15 minutes after the trailer comes off the tow vehicle. That only happens if the breakaway battery is charged and healthy. Test the system before each trip, and replace the breakaway battery if it won't hold its charge, especially after a hot summer.

Why does my van battery go flat on long drives north?

Usual causes include voltage drop over a long, thin charge cable, a smart alternator that lowers its voltage, a blown fuse in the charging circuit, a poor earth, or a charger cutting back because it's too hot. Test the circuit with a multimeter while the engine runs to find the real cause. A DC-DC charger with the right cable size fixes most cases.

Need an auto electrician in Adelaide?

Find local auto electricians and mobile services in the Adelaide directory, or start with your area: Northern Suburbs, Southern Suburbs, Inner West and Port, Western Beaches.

Run an auto electrical business in Towing a Caravan Out of Adelaide: Electrics for Long Trips?

• New to Ozautoelectrics? Apply for trade pricing on quality auto electrical parts.
• Already a trade customer? Log in and order parts at your trade price.
• Want more local customers? List your business on this site so drivers in Towing a Caravan Out of Adelaide: Electrics for Long Trips can find you.

Not confident doing this yourself?

There’s no shame in handing it over. A local auto electrician can diagnose the fault properly and get it done safely, especially for anything involving brakes, airbags, hybrid systems or air-con gas.

Get a quote from a local auto electrician Or shop the parts and do it yourself