With the advanced electronic components and increased amount of in-cab gadgets in big rigs these days, knowing the ins and outs of modern electrical systems is more important than ever for fleet technicians. Yet, some startling statistics bear out that this often-misunderstood system is not getting the attention it deserves and is subsequently eating away at many a company’s profits.
As the long-time Vice-chairman of Technology & Maintenance Council (TMC) electrical study group and president of the Rogers, AK-based Purkey’s Electrical Consulting, Bruce Purkey works with the biggest fleets in the nation--J.B. Hunt, Fed-Ex, Rider, Penske--where he sees some startling, across-the-board ignorance about electrical systems.
And it’s not just the big guys.
Purkey says the average score in a recent TMC electrical systems test was a paltry 37.6 percent; far from a passing grade. But he’s not just sitting in his office crunching numbers and wringing his hands about poor technicians--he is out in the field trying to prevent more of the horror stories he has experienced first-hand.
Recently, Purkey was training technicians from a major truck leasing company who just bought $5,000 worth of electrical system parts to try to repair a truck that wouldn’t start. The problem? Someone left off a ground cable from the starter to the engine block, but no one realized it until Purkey pointed it out.
“Instead of going through the normal path back to ground, (electricity) was going down the frame, up a cross-member, through the drive shaft and all the way back, generating about a two-and-a-half volt drop,” he says. “So (the technician thought) ‘Even though my alternator was perfect, could I ever get the right voltage of batteries? No. Were they always discharged? Yes. Did it cause me to burn up starters? Yes.’ And when the guy went to test it and he saw the alternator voltage was real low, he thought (to change the alternator). It was just a round-robin circle of replacing components, and it was a 35-cent fix.
“That happens all the time.”
Purkey helped put together TMC’s guidelines on voltage drops back in 1984 and is now in the process of re-writing it for modern applications. He says one thing has not changed throughout the years: Working in sequence is absolutely critical to accurately diagnose charging problems.
“First you’ve got to make sure your batteries are in a good state of charge,” he says. “The second thing is, do voltage drop checks on that charging cable. For years technicians checked the batteries maybe and the alternator but forgot about the cables. If my alternator has a setting of 14 and I’ve got a two-volt drop in my cables, do I get 14 volts in the battery? Hell, no. So can the batteries be charged, especially in cold weather? Hell, no. So I’ve got discharged batteries that cause me to have cranking problems, so everybody works on the wrong side of the circuit when it was just the cables that were bad. When it comes to electric systems, everybody does what they want to do, because you can’t see it.”
Travis Hopkey of the Santa Fe, CA-based Phillips Industries says a recent eye-opening trip to a major fleet garage made it all too clear how little some technicians know about simple wiring, much less complex electrical systems.
“One of the battery cables had shrink-tubing over it but they didn’t heat it to shrink it down, so you could just slide it up and down the cable,” Hopkey says. “You can imagine running down the road with the magnesium and calcium chloride that will just eventually eat (the cables) away, and (the rest of the technicians) will be scratching their heads later, saying ‘Well, what happened?’ People aren’t trained properly, or the training is inadequate.”
BACK TO BASICS
Careless techs have probably helped gain a sale or two for AIM, the Rancho Cordova, CA-based manufacturer of remanufactured starters and alternators for the heavy duty aftermarket. President Steve Seabourne says many electric system problems he sees are simply a result of under-diagnoses stemming from a lack of knowledge.