Towing a Caravan Out of Perth: WA Electrics Guide

This guide is for Perth caravanners and camper trailer owners, whether you are heading south for a week in the South West or north for a long run up the coast. It covers the WA trailer brake rules, brake controllers, plugs, keeping the van battery charged over long distances and the checks to do before you leave.

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Two very different trips out of Perth

Most Perth caravan trips go one of two ways. Heading south, you take the Kwinana Freeway past Rockingham and Mandurah, then the Forrest Highway towards Bunbury and the rest of the South West. It is a shorter trip with plenty of towns along the way, but holiday traffic and stop-start driving in the towns put the brakes and lights to work.

Heading north is a different story. Whether you take the Brand Highway up the coast or the Great Northern Highway inland, you are in for long days, big gaps between towns, summer heat and road trains sharing the road. A small electrical fault that would be a nuisance near Busselton can become a real problem hundreds of kilometres from the next town. That is why the electrics deserve a proper check before any northern trip.

The WA trailer brake rules

In Western Australia, trailer brake requirements are set out in the state transport department's Safe Towing information bulletin (IB-107). The brake rules are based on gross trailer mass (GTM), which is the load carried by the trailer's axles. Your towing limit is a separate question, based on the trailer's aggregate trailer mass (ATM) and the tow vehicle maker's limits. In summary:

• A single-axle trailer with a GTM of 750 kg or less doesn't need brakes.
• Over 750 kg and up to 2,000 kg GTM: brakes on at least one axle. Override (overrun) brakes are allowed up to and including 2,000 kg.
• Over 2,000 kg GTM: brakes on all wheels, operated from the driver's seat, so override brakes are not allowed.
• Over 2,000 kg GTM: a breakaway system that applies the brakes automatically if the trailer comes off the vehicle.
• The loaded mass of the trailer must never exceed its ATM, and you must stay within the tow vehicle's and towbar's ratings.

Rules change, so check before you go

The WA bulletin also covers couplings, safety chains and towing limits for vehicles where the maker's towing capacity can't be found. These details are updated from time to time, and the department has recently changed its name to the Department of Transport and Major Infrastructure. Read the current version of the bulletin before a big trip, and check your van's compliance plate so you know its real GTM and ATM rather than guessing.

Brake controllers for long WA runs

Most vans with electric brakes need an electric brake controller in the tow vehicle. On long northern runs, two features matter. First, a proportional controller that senses how hard you are slowing gives smoother, more even braking, which matters when you are braking from highway speed after hours of cruising. Second, a manual control you can reach easily lets you apply the van's brakes alone if a road train's wind blast or a gust starts the van moving around.

Set the controller's gain with the van loaded the way you will travel, not empty in the driveway. Recheck it if you change the load a lot, for example after filling the water tanks for a stretch with no reliable supply. The controller needs a fused feed from the battery that is sized for the current, and a solid earth. Our guide to installing an electric brake controller explains the wiring.

Plugs that survive dust and corrugations

The trailer plug is the link everything passes through: lights, brakes, and often charging. Red dust, corrugated roads and heat are hard on it. Pins loosen, springs lose tension and dust gets into the socket. Use a plug cover when the van is unhitched, check the pins are clean before you connect, and make sure the cable is clamped so it can't drag or rub on the drawbar.

If the van's battery charging feed runs through a 12-pin plug, the pin size limits how much current it can carry. Many WA caravanners run a separate Anderson plug with heavier cable for charging and keep the 7-pin or 12-pin plug for lights and brakes. See 7-pin vs 12-pin trailer plugs and how to wire an Anderson plug for the details.

Keeping the van battery charged between towns

On a long northern trip you may drive for hours each day and then camp somewhere without power. That makes charging while driving important, especially if you run a compressor fridge in the van. A DC-DC charger is the usual answer. It lifts the voltage that arrives at the back of the van after a long cable run, charges with the right profile for the battery type and works with smart alternators that drop their voltage once the starting battery is full.

Heat matters too. Mount the charger somewhere with airflow, away from the engine bay if possible, because many chargers reduce their output when they get hot. If your van battery still isn't charging on the move, read why a caravan battery may not charge while towing before replacing parts.

Before you leave Perth

Do these checks a few days before you leave, so there is time to fix anything you find. If you are heading north, do them again after the first rough day.

• Walk around the van with someone pressing the brakes and indicators. Check every light, including clearance and number plate lights.
• Roll forward slowly and use the controller's manual lever. You should feel the van brake.
• Test the breakaway battery and check the lanyard attaches to a solid point on the tow vehicle.
• With the engine running, confirm the van's battery monitor shows charge coming in.
• Check plug pins, the plug cover and cable clamps for wear or damage.
• Carry spare fuses, a few spare globes or LED lamps, electrical tape and a basic multimeter.

Getting work done before the trip

Brake controllers, DC-DC chargers and new plugs are common jobs for Perth auto electricians, and the cooler months before the winter trips north are busy. Book well ahead of your departure date. If you live south of the river, try our Kwinana and Rockingham or Mandurah pages. On the eastern side, near the start of the Great Northern Highway, see Midland.

Parts for this job

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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 Anderson plugs

Get it done: get a quoteDo it yourself: shop 7-pin trailer plugs

Questions Perth drivers ask

Does my caravan need electric brakes in WA?

Under the WA rules, a trailer with a GTM over 2,000 kg needs brakes on all wheels that can be operated from the driver's seat, plus a breakaway system. That usually means electric brakes and a controller. Between 750 kg and 2,000 kg GTM, override brakes on at least one axle are allowed. Check your van's compliance plate and the current WA towing bulletin.

What is the difference between GTM and ATM?

GTM, or gross trailer mass, is the weight carried by the trailer's axles when it is loaded. WA uses GTM to decide what brakes a trailer needs. ATM, or aggregate trailer mass, is the total loaded weight including the weight on the towball. ATM is used for towing limits, and the trailer must never be loaded beyond it.

How do I stop red dust getting into my trailer plug?

Fit a plug cover or cap and use it whenever the van is unhitched. Store the plug clipped up off the drawbar rather than hanging loose. Before connecting, blow out or wipe the socket and pins. If pins become loose or corroded, replace the plug rather than packing it, because a poor connection can cause flickering lights or weak brakes.

Why do my caravan brakes feel weak after a long day?

Common causes are the controller gain set for an empty van, a poor earth, a corroded or loose plug pin, or undersized brake wiring. Heat and dust can also affect the brake magnets and drums. Check the controller setting first, then the plug and wiring. If the brakes themselves are worn, have them inspected before you continue.

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