For a lot of mechanics, diagnosing the cause of a failed charging system has about as much appeal as a lecture on quantum physics. This might explain why so many charging failures are misdiagnosed and so few mechanics become physicists.

Inadequate training, indifference and the constant push to move more jobs across the shop floor -- these are among factors responsible for the countless alternators and batteries prematurely pulled from service because they were thought to be faulty.

"Delco Remy and Leece-Neville people claim that nearly half of all returned alternators are still in good working order," says Bruce Purkey, owner of Purkey's Fleet Electric in Rogers, Ark. This volume of needless activity is costly, frustrating and time consuming for maintenance personnel and component makers.

Slow and frustrating
Purkey blames the problem on traditional testing methods, which involve clip-on ammeters, voltmeters or multimeters, carbon-pile load testers and a few mathematical calculations. The full set of procedures can take several hours, not including the time needed for battery charging, the first step in any thorough diagnosis. Often, though, mechanics shy away from digging too deeply into the system. They'll just swap parts, hoping the vehicle doesn't return with the same symptoms a day or two later.

Several devices have come out recently to speed and simplify charging system work. Purkey helped develop two of them: the Intelli-Check alternator analyzer, sold by Delco Remy, and the InSyght battery and volt-drop tester, sold by Auto Meter. Both units are hand-held and use computer chips to perform thousands of split-second measurements that check component performance.

"With these tools, a 16-year-old kid is as good as a guy with 32 years of experience," Purkey says. "That's because I poured 30 years of experience into microprocessors that do everything but hook up the cables."

Faster, more efficient
The Intelli-Check, which sells for $450 to $500, is designed so that one person can test alternators. The task normally requires two: one in the driver's seat operating the engine, the other standing by the alternator reading current levels through a clip-on ammeter or multimeter. With Intelli-Check, mechanics simply connect the device's two alligator clips to an alternator's output and ground terminals, then bring the unit into the bus while they start, idle and rev the engine. A series of lights indicate the test results.

"It's a very complex machine that actually changes its values as electrical frequencies change," Purkey says. "But it's very user friendly."

InSyght is similarly friendly, although it has four alligator clips instead of two. Jack Lembke, Auto Meter's division sales manager, says InSyght's ability to electronically measure voltage drop is faster and more accurate than traditional methods -- and it encourages mechanics to perform the test more frequently.

"The reason so few people do voltage drop tests is that they're complicated, and most technicians aren't sure what the appropriate numbers are supposed to be," he says. "Our device has a screen that prompts them through the process. Plus it gives them the results in plain English: good or bad." InSyght is available with a small printer that can receive infrared signals from 50 feet. The combination is packaged in a hard-shell case and sells for about $700.

Easy battery testing
Corey McCormack is a veteran in the war on charging system trouble, and over the years he's used a number of tools to find and solve it. As the maintenance manager for Hunt's Bus Co. in Anoka, Minn., he is especially familiar with battery problems, in part because his company's routes are fairly short and involve a lot of stop-and-go traffic. He says that during the winter, when lights and heaters are operating constantly, buses will commonly return to the yard before their batteries are fully recharged.

In the past, he used a carbon-pile load tester to gauge the condition of weak batteries. But it required a good amount of time and labor because the batteries often had to be pulled from service and charged for 24 hours before they could be properly tested. Recently, McCormack invested in an Accuracy Plus digital tester made by the SPX Corp. and sold by Mac Tools and others for $500 to $600. The device allows him to check batteries at almost any state of charge in less than 30 seconds.

During a test, the Accuracy Plus applies three low-amp loads to a battery. The resulting response is then fed through computer chips, which match it against a range of performance characteristics. According to Scott Krampitz, an SPX product manager, the system can identify nearly every possible failure mode of a battery just by watching its recovery ramp up.

Krampitz says the Accuracy Plus is selling well to mechanics of all stripes, but it's particularly popular among battery manufacturers and dealers because it enables them to quickly determine whether a customer's warranty claim is justified. He says this has led to "significant reductions in those costs."

Don Dilks, regional manager of maintenance for Laidlaw Education Services in Omaha, Neb., wouldn't be surprised. "In theory," he says, "good test equipment should lower costs." Laidlaw operates Hunt's Bus Co., and Dilks approved McCormack's purchase of the Accuracy Plus. He says he's planning to buy the tools for all of his shops by summer.

While he's not overly impressed with electronic gadgets, Dilks believes there is some practical advantage to using them. "You can do most of the same jobs with basic tools," he says, "but [the new devices] are better because they lower the chance of error. Load testers, for example, have been around forever, but people really don't understand how to use them, don't get the proper training or they simply forget. Well, these new devices let you test systems without any kind of training. All you need to do is follow the menus. The machines tell you what they need."

Good spec'ing helps
Dilks says the best method of reducing charging system trouble actually begins long before any maintenance is required: during the spec'ing of a bus. "You've got to make sure you order the right alternator and battery set up for your operation," he says, "otherwise you're going to have plenty of problems."

The information below applies to the testing of a typical bus charging system. Always seek expert advice before starting such tasks if you're unfamiliar with them. Use caution anytime you're working on electrical components. Eye protection is a must. The Accuracy Plus and InSyght are capable of several types of tests, but each device is described here performing just one.

Traditional -- Make sure the batteries are in good condition and fully charged. Have an assistant start the engine. Connect a multimeter to the alternator's output and ground terminals. Standard multimeters will provide a voltage reading, which just indicates whether the alternator is, or is not, generating some amount of current. Ask your assistant to turn on the vehicle's lights and heater fans, then increase the engine's speed. The voltage reading should remain fairly constant around 14 to 14.5. Anything outside that range merits further investigation or possibly a new alternator.

Intelli-Check -- Connect the cable plug to the device. With the engine off, connect the cables to the alternator's output and ground terminals. The device will perform a brief internal test, during which time its lights will go out. About four seconds later the lights will illuminate. Remove the batteries' surface charge by turning on the headlights for a minute or so. Start the engine and let it idle briefly. Then accelerate to governed speed for 10 to 15 seconds. Return to idle speed. Repeat the process, but this time with lights and heater fans turned on. One of three lights will indicate the results: green for normal, red for defective, blue for low battery voltage. In the latter scenario, you will need to fully charge the batteries and retest.

Traditional -- Batteries must be fully charged and tested individually. Disconnect the cables and clean the battery posts. Attach top post adapters to Group 31 batteries. Remove surface charge by turning on headlights for a minute or so. If the battery is disconnected, apply a brief 20-amp load with the carbon-pile tester. Connect the tester's cables to the battery. Adjust the amperage load to half of the battery's CCA rating. Apply the amp load for about 15 seconds and watch the load tester's meter, making sure the reading doesn't drop below 9.6 volts. The exact threshold will vary by the battery's temperature. Refer to information supplied with the load tester. Repeated tests will discharge a battery.

Accuracy Plus -- Batteries must be tested individually. Disconnect the cables and clean the battery posts. Attach top post adapters to Group 31 batteries. Turn on device and connect the cables to a battery. Using the up-and-down arrows, select "battery test." Scroll through the sub menu and select the battery's CCA rating. "Wiggle clamps" will appear in the display. Press "go." Wait a moment while a reading is taken. The results will appear in the display. Repeated tests have no effect on battery charge.

Traditional -- Closely inspect all cables and their connections. With the bus shut off, connect a carbon-pile load tester to the alternator's output and ground terminals. Adjust the load tester until it's drawing an amount of amperage equal with alternator's rating (120 amps, for example). Connect a voltmeter or multimeter to the batteries' main lead and ground terminals. Newer load testers have extra cables for doing volt-drop tests without using another device. Measure the voltage at the batteries. Turn off the load, and connect the voltmeter to the alternator's output and ground terminals. Apply another amperage load equal to the alternator's rating. Measure the voltage at the alternator. The first and second volt readings should be within a half-volt of each other.

InSyght -- Closely inspect all cables and their connections. Temporarily connect a single battery when testing multiple-battery systems. Attach top post adapters to Group 31 batteries. Turn on the tester. Use the up-and-down arrows to scroll through the main menu shown in the display. Select "voltage drop" and press "Y." Scroll through the sub menu, select "charging cables" and press "Y." Connect the large cables to the alternator's output and ground terminals. Connect the small cables to the battery posts. Wait a few moments for reading to be taken. InSyght measures the volt drop in both positive and negative circuits simultaneously. The results, appearing in the display, will show the percentage of volt drop or indicate (in amps) the current carrying capacity of the cable. Author Paul Hartley is a freelance writer in Northfield, Minn. He is also the equipment editor at Overdrive, a trucking magazine.

Originally posted on School Bus Fleet