Truck and Fleet Electrics in Kewdale and Welshpool

This guide is for fleet managers, owner-drivers and workshop staff running trucks and commercial vehicles out of Kewdale, Welshpool and Perth's other industrial areas. It covers how 24V systems work, the most common electrical faults in freight and delivery fleets, and the checks that keep vehicles on the road.

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Perth's freight heartland

A lot of Perth's freight moves through the industrial suburbs east of the city. Kewdale is bounded by Perth Airport to the north and is home to the Kewdale Freight Terminal. Welshpool, to the south, is one of Perth's traditional industrial suburbs, valued for being close to both the airport and the CBD. Further out, Malaga and Osborne Park in the north, and industrial areas such as Canning Vale, Bibra Lake, Henderson and Kwinana in the south, run their own share of trucks, vans and utes.

Fleets in these areas work hard. Delivery trucks stop and start all day, prime movers cover long distances, and refrigerated vehicles run their cooling units around the clock. Every one of those jobs puts load on the electrical system, and a single electrical fault can take a vehicle off the road for a day or more.

How a 24V system works

Most heavy trucks and many larger commercial vehicles run a 24V system. The usual setup is two 12V batteries wired in series: the positive of one battery connects to the negative of the other, and the remaining two terminals give 24V. A 24V alternator charges both batteries together.

A 24V system has real advantages for heavy vehicles. For the same power, the current is half what a 12V system would need, so starter motors crank large diesel engines with less strain and cables can be smaller for the same job. But it also brings its own problems, and many of them come from treating a 24V truck like a 12V car.

Keep the batteries matched

In a series pair, both batteries carry the same current, so they need to be the same type, size and age. If one battery is weaker, it drops in voltage first and gets pushed harder while charging. Over time it fails, and it often takes the other battery with it. When one battery in a 24V pair fails, replacing both together is usually the better choice.

Corroded or loose terminals cause similar trouble. The link cable between the two batteries carries the full starting current, so a poor connection there causes slow cranking and uneven charging. Check the link cable and every terminal at each service. Our guide to cleaning corroded battery terminals applies to trucks as well, and testing a battery explains what the readings mean. Test each battery in the pair separately.

Don't tap one battery for 12V

Drivers and fitters often want to run 12V accessories in a 24V truck: a fridge, a radio, a phone charger, a dashcam or a telematics unit. The tempting shortcut is to take a 12V feed from just one of the two batteries. Don't. That battery then supplies the 12V load on its own, so it discharges more than the other. The alternator charges both as a pair and can't correct the difference, so the pair drifts out of balance and both batteries wear out early.

The right way is a 24V-to-12V converter (sometimes called a voltage reducer), sized for the total 12V load with some headroom. For loads such as a 12V fridge, a quality converter rated for continuous use is worth the extra cost. Fuse the converter's input close to its supply, and check where to put the fuse when wiring an accessory if you are unsure.

Common faults in Perth fleets

Most fleet electrical breakdowns come back to a handful of causes. Knowing them helps you brief drivers and plan maintenance:

• Starting problems from weak or mismatched batteries, or a corroded link cable.
• Alternator faults, often from worn brushes, a failed regulator or a slipping belt.
• Chafed wiring where looms pass through the chassis or cab, especially behind the cab where vibration is worst.
• Trailer lighting and plug faults from worn pins, water ingress and corroded earths.
• Accessories wired in by tapping into existing circuits, which overloads them or causes unexpected battery drain.
• Heat damage to batteries and wiring in the summer months, when engine bays and parked trucks get very hot.

Trailers, plugs and earths

On prime movers and rigid trucks towing trailers, the trailer connection is one of the most common fault points. Plugs are connected and disconnected many times a week, so pins wear and springs loosen. Dust and rain get in. A poor earth at the plug can make several trailer lights act strangely at once.

Clean and inspect plugs and sockets regularly, replace worn ones rather than packing them, and make sure the trailer has a solid earth back to the truck. Our guide on why trailer lights aren't working covers the fault-finding approach. Trailers with ABS or EBS also carry data and power for those systems, and that work is best left to a heavy vehicle specialist.

A simple fleet electrical routine

A short electrical check at each service, plus a daily walkaround by drivers, catches most problems before they leave a truck stranded. Ask drivers to report slow cranking, flickering lights or warning lights straight away rather than at the end of the week. At service time, test both batteries, check charging voltage at idle and under load, inspect the link cable, battery hold-downs and main earths, and look over looms for chafing. Keep records, because a battery or alternator that keeps failing on one truck usually points to a wiring or charging fault rather than bad luck.

Finding fleet support in Perth

Many auto electricians in Perth's industrial areas work on trucks and commercial vehicles, and some will come to your depot so vehicles don't need to be moved. Start with our pages for Kewdale and Welshpool, or Malaga if your depot is in the north.

Parts for this job

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Questions Perth drivers ask

Can I run a 12V fridge in a 24V truck?

Yes, but not by connecting it to one of the two batteries. That unbalances the pair and shortens the life of both. Use a 24V-to-12V converter rated for the fridge's current with some headroom, and choose one rated for continuous use. Many fridges also run on 24V directly, so check the fridge's specifications before you buy a converter.

Should I replace both batteries in a 24V truck at once?

Usually, yes. In a series pair, both batteries carry the same current, and a new battery paired with an old one ends up working unevenly. The weaker battery fails sooner and can take the new one with it. If one battery is very new and tests well, a professional may advise otherwise, but replacing the pair is the safer default.

Why does my truck crank slowly when the batteries test fine?

Check the cables and connections. A corroded or loose link cable between the batteries, a poor main earth or a worn starter cable can cause slow cranking even with good batteries. Voltage drop testing while cranking shows where the loss is. A tired starter motor can cause the same symptom, so test it if the wiring checks out.

How often should fleet vehicles have their electrics checked?

A sensible approach is a battery and charging system test at every scheduled service, with a daily walkaround by drivers to check lights and warning lights. Vehicles that stop and start all day, run refrigeration or work through Perth's hottest months may need extra attention. Keep records so repeat faults on one vehicle are easy to spot.

Need an auto electrician in Perth?

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