Resolving electrical faults

Electrical problems are inevitable for any vehicle, but even more so when that vehicle is subjected to the harsh environment of a quarry. Toby Clark speaks to master technicians at onsite workshops to see how they approach tracing, analysing and repairing electrical faults

Derbyshire's Longcliffe Quarry celebrates 100 years of operation in 2027, but shows no signs of slowing with age: the site currently produces 10,000t of processed limestone product every day. Responsible for delivering product to customers is its transport fleet of rigids and 6x2 tractors. Averaging 65,000 miles a year, the trucks traverse the whole of Great Britain; 6x2 tractors with lightweight midi-lift axles pull powder tankers.

Aggregate is also delivered by tipper truck, a fleet augmented when demand requires by a few hire companies near the Matlock operation, owing to the reactive nature of that business. “We might have a customer wanting 300t today. Spikes in demand are challenging to forecast,” states logistics manager James Hopkinson. “Uptime is a massive issue, and the garage does a great job in turning around the trucks quickly.”

That function is carried out just down the road from the quarry in Longcliffe’s Curzon Lodge Transport Garage. It’s a recently-built dedicated four-bay, four-pit workshop fitted with Maha roller brake testers, local exhaust ventilation and overhead reels for air and hydraulics. Garage manager David Smith explains that the organisation has always believed in investing in engineering resource to provide its own operational independence. “I’ve worked here for 38 years and we have always had our own maintenance department for transport,” he says. “We have always found it better to have our own technicians onsite. If a vehicle breaks down, you could be waiting days or even weeks if you rely on an external main dealer. Our set-up provides us with the flexibility to organise our own maintenance.

“Plus, we run various types of tractors and rigids and powder tankers; it would be difficult to find a one-stop shop that would meet all of our maintenance requirements,” he adds.

Longcliffe has also invested in its technicians directly, firstly by training them through a three-year Level 3 HGV apprenticeship with Stoke College. After successfully completing their apprenticeship, the team of five – including garage team leader Josh Griffiths and technician Morgan Peel – went on Volvo Trucks training. Last year they were accredited to IRTE’s service and maintenance technician qualification. The Transport Garage is also IRTE accredited.

The Volvo training came off the back of an order in 2022 for 10 vehicles – three 8x4 tippers and seven tractors. Hopkinson states that the organisation tends to buy trucks outright and sell them on after five years, although supply chain delays caused by COVID have impacted those figures somewhat, he admits. Another novelty is leasing; Longcliffe has also begun arranging 3-5 year truck leases, when favourable terms are available.


Given their training and facilities, Longcliffe’s technicians are ideally placed to tackle anything in varied roles that range from mending and replacing tyres to troubleshooting, diagnosing and fixing electrical faults. Griffiths reckons electrical issues are “probably more frequent now than they ever have been, there’s so many systems… if you're a technician, you see them on a daily basis”.

What proportion of electrical problems can be diagnosed using the regular diagnostic system, rather than the traditional methods? “I’d say it’s probably 50-50,” says Griffiths. “At the end of the day, all a diagnostic computer will do is point you in the right direction. If it says you’ve got a fault with a NOx sensor, you’ve still got to test your power to it, your ground to it, your CAN wires between that and the ECU… it’s not as easy as plugging in a new NOx sensor.”

Griffiths’ colleague, Morgan Peel, says that after looking at the diagnostic system (and Longcliffe is currently using Jaltest, alongside Volvo’s system), it becomes a process of elimination. “Obviously, you start with simple things such as fuses – make sure nothing daft can catch you out – and from there you probably look at the component itself,” reasons Morgan. “And make sure it’s getting the voltage and the ground it should be.”


To the south-east of Longcliffe, Chris Sharman is workshop manager for Heidelberg Materials at the Ketton cement works in Rutland, where eight technicians (plus an apprentice) service around 60 vehicles and 100 trailers, as well as vehicles from other depots.

“We've got one or two items that we substitute, just to eliminate: before we purchase any items, we can pop a new solenoid valve on, make sure that’s working,” says Sharman, describing his approach to electrical troubleshooting. “We can even replace sections of wiring. We’ll work back from the issue: we’ll take it back to each connection and ultimately through to the ECU.

“One of the best bits of equipment that we have is a really good multimeter and a good, reliable wiring diagram,” he adds. “You can lay that out and have a chance of tracing it back to various locations where there may be another connection.”

Most diagnostic systems combine the schematic wiring diagram with pictures of the components and their location on the vehicle, but Sharman is sceptical about where wires end up. “Many vehicles have a different approach, shall we say, to where things are fitted, and some manufacturers are not helpful: they’ll use similar-coloured wires, just numbered.”


Returning to Derbyshire, Griffiths stresses the importance of tried-and-tested techniques. “The old ways sometimes are the best ways,” says Griffiths. “It’s easy to get caught out with a wire that's starting to corrode but hasn’t fully broken. Your multimeter is still going to show 24V. If it’s badly corroded, your voltage is going to start dropping, but first you’re going to see a drop in current flow. And that’s where a bulb comes in handy because, obviously, if that wire can’t pass enough amps to light the bulb, you’ve pinpointed a corroded wire.”

Technicians can get tools with a test light that represents a load, but Griffiths says you can use a simple sidelight bulb: “You don’t want to use a high-output headlight bulb, because the current it can draw may be more than the wiring is rated for. It helps having a wiring diagram because that will tell you how much resistance a component will have.”

“Usually trailer wiring faults are pretty quick and easy to diagnose,” reveals Peel. “It’s probably going to put one or two sidelights out down one side and that basically straight away narrows it down to that area.”

“We’ve both got Power Probes,” he adds. “Very accurate and handy, because you’ve got a constant good earth.” Power Probe is a trade name, but similar tools are available. Essentially it’s a circuit tester with positive/negative indicator lights and tones – and many of the functions of a multimeter. But the difference is that it’s connected to the battery terminals via a long lead – and when you press a button, the probe tip can supply either a full positive voltage or an earth connection, to test components or wiring in situ. You need common sense – apply 24V to the wrong component and it could be fried – but “the Power Probe is perfect for good earth and it’s a visual thing as well; you can see the voltage on the screen.”

Another tip from Sharman is to mind the earthing arrangements. “ECUs and the microvoltage that they use, if you haven’t got a good earth connection, can easily create problems,” he says. “The engine and chassis earthing needs to be pretty good.

“A lot of the switchgear and wiring, along with the various ECUs and modules, are all fantastically waterproof – unfortunately, they’re not power-washer-proof,” adds Sharman. “The wiring does go through the mill, with the dust, the washing, oil and grease ingress and the winter/summer cycle on the roads. Also, the wiring and some of the connections can become brittle. We have seen issues with injector wiring on the engine itself, where it goes into the rocker housing and then on to the injectors. Those looms can play up because they’re in an adverse atmosphere that experiences heat, oil, moisture and vibration. And if you have an AdBlue leak, you’re in a world of pain because it’s very corrosive to wiring.”


Sharman says technicians should understand that even the best-made vehicles will have limitations. Electronic components are built to a cost and even solid-state assemblies will deteriorate with vibration. “We’ve experienced ECU problems because of how they’re made,” he adds, but points out that “the manufacturers listen – they do improve, and fill them with gel to prevent that vibration and solder joints drying out”.

When it comes to protecting electrics, Peel says Longcliffe Quarry uses a spray water repellent on battery terminals or suzie sockets – “things that get taken off and put back on regularly”. Other parts may be treated with a dielectric grease.

Returning to Rutland, Sharman advises that quality electrical systems need quality electrical maintenance. “If you carry out a repair, ensure that it’s carried out to a good standard, using correct connections and making sure it’s watertight,” he says. “There are wiring repair solutions you can solder together and heat up to form a watertight bond – but the best solution is to replace as opposed to repair. If you’ve got a section of wire and there's a break in it, replace the whole section from coupling to coupling – it is far more robust.”

The last word goes to Griffiths: “A broken wire is a physical fault, so you use the multimeter to check for continuity and if there is none, you know it’s a broken wire. They can be difficult to track down but, at the same time, they are a relatively cheap fix. Whereas faults with sensors or ECUs, which could be intermittent, are the most annoying.” He says that accurately pinpointing those involves taking the time to carry out road tests and scrutinising fault records in the diagnostic tool.

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