Do techs understand the fundamentals of electrical system diagnosis?

Imagine this scenario: you have a truck that is in the shop for a hard-cranking issue. The technician replaces the battery, replaces the starter, and replaces the alternator, but the truck keeps coming back to the shop with the same problem. Finally, the technician realizes that it was a bad cable, and all of those extra parts were replaced when they didn’t need to be.

What went wrong in the above scenario? The technician didn’t fully understand the strategy behind electrical system diagnostics, and fell into the trap of what John Renno, manager, Center of Excellence, Isuzu Commercial Truck of America, calls “swapnostics.”

“One of the struggles in this industry is that many technicians haven’t been taught very well how to apply a best practice or a theory. What they’ve been taught is, ‘when you see this symptom, replace this part,’” Renno explains.

When electrical systems are misdiagnosed, the repair doesn’t work and the initial problem will recur, leading to increased vehicle downtime. If a technician replaces a part that hasn’t failed, it can cause problems for the fleet. For example, if they try to turn the item in for warranty and the part is tested, the warranty claim will be rejected, says Bruce Purkey, founder and chief creative engineer for Purkeys, and a consultant for Auto Meter Products. Purkeys develops solutions for charging and protecting vehicle batteries.

“Roadside breakdowns and unnecessary repair expenses can result from misdiagnosis,” Purkey stresses.

In addition, when technicians replace parts that don’t need to be replaced in an attempt to further their diagnosis, it can make it more complicated to isolate the root cause of the issue, adds Keith Littleton, trainer and owner of K&D Technical Innovations. Littleton has worked in the industry as a trainer and technician for over 30 years.

“Going down the wrong path of misdiagnosis starts this kind of evolving situation that makes it really difficult to diagnose the root problem because you never really know where the issue started from,” says Littleton. “A lot of times, technicians are missing really small things. Probably 65 to 70 percent of the time, it’s very basic problems that get overlooked, and many parts get replaced that aren’t necessary.”

Ensuring that technicians have the correct tools to diagnose a vehicle, knowhow to use their tools correctly, and have the training to effectively diagnose an electrical problem can help minimize misdiagnosis issues and maximize vehicle uptime.

The basics of electrical systems

Gerald Tabas, ASE Master Technician for Power Probe Tek, compares a vehicle electrical system to the human body’s circulatory system.

“The battery is the heart of the vehicle,” he explains, and “wiring runs like veins, allowing voltage to travel to various parts of the vehicle, such as switches or motors.”

Like blood flowing from the heart to the rest of the body, electrical current flows under pressure to the various components being powered—this pressure is measured in volts. The total strength of the electric current is measured in amperes, often shortened to amps. As electricity flows, it encounters resistance, which is measured in ohms.

These three measurements of electricity – voltage, amps, and resistance – are a key part of understanding electrical system diagnosis, explains Isuzu’s Renno.

“If you can understand those three components together, you can do very well at diagnostics. If you can figure out two of those measurements, you can understand all three. If you know the voltage and amperage, you can figure out the resistance, or if you know the voltage and the resistance, you can figure out what the amperage is doing.”

Evaluating and training technicians

“One of the most important starting points for technician training is to go back to the basics, and for electrical diagnostics, part of that is simply training technicians how to use a multimeter,” says Larry Rambeaux, Sales Manager for Purkeys.

He notes many managers that contact him for training believe their technicians are ready for an advanced course in electrical work and are above average. He cites one example where a fleet was adamant that its technicians were too advanced for what Rambeaux calls “Multimeter 101.” But, when given a pre-test to gauge the technicians’ actual skill level, the fleet was shocked by how low the scores were.

This is a common issue, Rambeaux says. Last year at the TMC SuperTech technician skills competition, of the top 116 technicians that competed, the average score was only 66 percent. “There is plenty of room for improvement,” he emphasizes.

An alternative to subjectively judging technician skill level based on limited observation is to have technicians take standardized tests. There are a variety of standardized tests available – the ASE certification tests are one example. TMC is currently working on a technician test as well.

“Test your technicians and determine what skill level they have. That’s what you’ve got to base your training on,” Rambeaux says. “Then you’ve got to keep it updated and make sure you’re retesting your technicians to make sure they are learning and identify problem areas. It can even be part of the pre-hiring criteria, so you know what you’ve got when starting new employees.”

Once a fleet has determined the current skill level of its technicians, the next step is to find training resources to help their technicians more effectively handle electrical diagnostic work.

“Most people are in such dire need of a good technician that they’re looking for a magic silver bullet or a couple-day class where we can get technicians up to speed, but electrical diagnostics is not something you can a take a couple-day class and get really good at it,” Isuzu’s Renno adds. “It’s something that takes years of practice. Fleets have to assess where the technicians are at, and then come up with a plan to grow them beyond that. It’s not a quick process.”

There are a variety of training sources available to fleets looking to help their technicians improve, and the best source will depend on what areas the technicians in a fleet are struggling with. Tool and equipment manufacturers offer electrical training that focuses mainly on how to effectively use their tools and equipment for electrical diagnosis. This type of training can be helpful in improving diagnostic efficiency, but only if the technician already understands the basics behind electrical diagnostics.

Another resource to consider is the vehicle manufacturer. Some, like Isuzu, offer electrical training as well. Renno cautions, however, that this training does not always help technicians who don’t already understand basic electrical diagnostics. “As a general rule, manufacturer training assumes that technicians already have a grasp of basic electrical diagnostics,” Renno says. “It focuses mainly on the specific information that is unique about their brand.”

“What I have found over the last few years is that the basic foundations that we were assuming the technicians had, weren’t there,” he adds. “So [Isuzu] developed a basic electrical class that we have to teach before the technician can take a diesel diagnostics class, because we were struggling to teach advanced diagnostics because they didn’t have a firm grip on the basis of electrical work.”

There are also a variety of online courses, videos, and computer classes available. However, K&D Technical Innovations’ Littleton cautions that while these courses can be helpful for introducing the theories and basic concepts behind electrical diagnostics, many technicians don’t benefit as much from the computer training as they do from hands-on training.

“Online courses can help, but I’d call those pre-course work,” he says. “You can do those before you get to class, but a lot of technicians need to put their hands on it to fully understand the training.”

Littleton adds that OEM training can be helpful for diagnosing one specific vehicle type, but for technicians that work on various vehicle types, a third-party trainer will typically focus more on general technician improvement type training.

“That means it’s not specific to one product line – it's generic across all product lines, and teaches them how to diagnose everything, not just one specific way of doing it,” he says.

“Train and evaluate technicians via real-time Wi-Fi reporting to ensure all technicians are following company repair procedures,” Purkey suggests. “Simply buying a tester is not enough. Are your technicians using the tester? Are they making the repairs as expected?”

He adds that even the best-trained technicians will struggle with electrical diagnostics if they do not have access to information on the systems and diagnostic procedures on the equipment the fleet is currently using. Every OEM and system is different, and it is hard for technicians to diagnose a system if they don’t have the information on how it is supposed to operate. Fleets should make sure that technicians have access to accurate OEM information and wiring diagrams, and that they have the tools and equipment they need to effectively diagnose vehicles.

“Electrical diagnostics is the toughest task a technician will ever face,” says Steve White, president of Electronic Specialties. “There are so many different OEMs with different schematics, and that makes it particularly difficult to stay abreast of all the nuances and changes that happen almost daily. It’s essential for techs to take time to research the problem and the technical information provided.”

Common errors for misdiagnosis

Aside from a general lack of training or understanding of electrical systems, there are a few common areas of confusion that can lead to misdiagnosis.

• Voltage drop. One of the most commonly misunderstood diagnostic concepts in electrical diagnosis is voltage drop, says Purkeys’ Rambeaux. “You can have a wire that’s damaged or corroded, and if you put a voltmeter at the end with nothing connected, you can see perfectly good voltage. But as soon as you have a load on it, that voltage may drop.”
  When checking a wire or circuit, Rambeaux stresses that technicians should be testing under the same load that the wire is expected to handle in normal operation. “If that wire in normal operation has to handle 5 amps, or 40 amps, or 100 amps, we need to put a load on it somewhat similar to that. So, circuits always need to be tested under load, but you also have to make sure you understand what that circuit should be loaded at.”
• Relying too heavily on one measurement. A problem that Isuzu’s Renno has noticed with inexperienced technicians is that they don’t understand how voltage, amps, and resistance work together and only focus on one measurement – oftentimes voltage. If a technician only focuses on one measurement, they are only seeing one-third of the picture. If they use that limited information to make diagnostic decisions, they are more likely to misdiagnose the issue, because they don’t fully understand what is happening in the electrical system.
• Not using the wiring diagram to inform the diagnostic process. A wiring diagram is the technician’s roadmap to figuring out electrical issues, Renno says. “The biggest mistake I see technicians make is they don’t read a wiring diagram first. They need to identify the circuit on the wiring diagram, identify the points they need to check, [and] decide what voltage, amperage, or resistance they are checking there. Then when they go to the truck, it’s a yes or no answer.”
  He adds that a lot of technicians make the mistake of going to the truck first, taking an arbitrary measurement, and then going back to the wiring diagram to try to find out whether the measurement was good or bad. If they go to the wiring diagram first, they can use strategy-based diagnostics to isolate the issue.
• Using static measurements instead of dynamic ones. Using test equipment in static situations can allow technicians to misdiagnose circuitry because it gives them a false sense that components are okay, says K&D Technical Innovations’ Littleton. When you take a dynamic measurement while the circuit is operating, you get a true idea of what is happening in that system.
  “One thing that some technicians miss the boat on is they avoid checking things dynamically, because in electrical systems, everything is connected, and they believe that to attach themselves in a circuit in a way that sometimes could cause damage to the circuit. A lot of technicians don’t understand that you can do things inductively with an amp probe where you can go around the outside of a wire with an amp probe without being intrusive in the circuit," Littleton explains.
• Relying too much on OEM software and scan tools. “Some technicians tend to rely on the OEM software and the scan tools to figure out root causes of problems,” Littleton says. “A lot of times, root causes are found by testing dynamically, not by looking at a scan tool or looking at software. You can’t just plug in the scan tool into the truck and expect it to say, ‘Go to connector number three, there’s a high resistance there.’”
• Assuming the wiring harness is okay. “Most diagnostic procedures assume that the wiring harness is okay,” Renno says. “That’s where technicians can get tripped up and go through the service procedure and replace a lot of parts, and then they get to the end and realize that the wiring was what was wrong in the first place.” With rust and corrosion, wires can deteriorate over time, so technicians should be sure to test that the wires are working correctly before replacing larger parts.

Utilize technician talent effectively

While fleets can improve their overall technician education level, not every technician has an aptitude for electrical diagnostics, cautions Electronic Specialties’ White.

Isuzu’s Renno adds that fleets need to assess the skills and talents of every technician in the shop and use that information to keep things running smoothly. “Different technicians have skills in different areas, and fleets need to figure out how to take advantage of each technician’s skills and minimize their weaknesses. So that means that some technicians may just be changing parts, while others focus on diagnostics. It’s not necessarily bad if everybody in the shop can’t do diagnostics.”

Renno describes a strategy that he has seen effectively employed in some large shops that he calls “triage.” Whenever a vehicle comes in to be worked on, the shop has a highly skilled technician who is good at diagnostics assessing the vehicles. Once the vehicle has been diagnosed, the faulty part can then be replaced by a less experienced technician.

Renno says that this strategy works well because it ensures that vehicles are being diagnosed correctly and the root cause of the issue is being addressed, instead of just replacing parts and hoping something works. He adds that in order to become adept at electrical diagnostic work, a technician must routinely diagnose vehicles. “Electrical diagnostics is a little bit different than other repairs. It’s not like tearing a component apart, where once a technician understands how to do it, they usually won’t forget even if they don’t use the skill for six months,” he explains. “Electrical work is philosophical. There’s theory involved. It is a learned skill, and it has to be exercised.”

Conclusion

When technicians misdiagnose electrical problems in vehicles, it can be costly for the fleet. If fleets notice that technicians are experiencing a lot of comebacks, taking an extensive amount of time to diagnose electrical circuits, or are replacing components to help diagnose circuitry, these are signs that the technician may need extra training to diagnose electrical systems more effectively.

Electrical systems are complex, and many technicians can benefit from training that covers diagnostic theory and tool usage, in addition to OEM-specific and advanced training. Having an accurate measure of technician skill level, investing in technician training, and effectively utilizing the pool of technician talent that the fleet has available can help improve electrical diagnostics and maximize uptime.