Winning the power struggle

Keep your trucks moving by catching electrical problems early and spec’ing the right alternators and starters.

With overnight shutdowns becoming more and more the rule, it’s more important than ever to enable the driver to rely on the truck’s ability to start in the morning. The most critical part of ensuring alternator and starter reliability, experts agree, is proper testing and maintenance of the entire electrical system.

“A common problem that we see is that the vehicle’s charge/start system is not analyzed and viewed as a system,” says Eric Karr, national account manager for Mitsubishi Electric. Each component’s performance affects the operation and longevity of the other components within the system, and focusing only on one component often results in a misdiagnosis or repeated failures before its design life has ended, Karr says.

Fleets should use the appropriately rated alternator for its application to ensure the product’s longest possible life, says Orlando Braga, senior application engineer for Denso Sales California. “They also should check battery condition regularly and discard batteries that no longer take a charge or show physical wear,” Braga says. Also, checking for proper cable connections in the charging system – including the alternator, starter and battery – as well as replacing old cables that are worn and create high resistance can ensure correct alternator life, he says.

Many problems with the alternator have their source from elsewhere within the electrical system, says David Canfield, director of global marketing for Leece-Neville, a division of Prestolite Electric. “It is important to consider the entire system when developing your preventive maintenance program,” Canfield says. “The alternator, starter motor, battery, cabling and all of the electrical loads make up the electrical system, and an issue anywhere within that system will affect the life expectancy of all the individual components within that system.”

Troubleshooting tips
Worn batteries take more energy to recharge than good ones, and doing so also increases the alternator’s operating temperature. The alternator’s internal resistance increases with temperature, reducing its output, so bad batteries quickly snowball into a serious shortening of alternator life.

“Checking and replacing alternator belts, ensuring the correct tension, and using the correct alternator pulley and belts also will help ensure the correct alternator life,” Braga says. A slipping belt creates tremendous heat, which the steel shaft carries to the bearings, causing the grease to boil off and resulting in almost immediate bearing failure.

“High cable resistance can lead to chronic undercharging of batteries, which shortens their service life and requires frequent replacement,” Karr says. “By properly understanding the start/charge system as a whole, the offending component can be identified and corrected. In this case, it’s a wiring issue.” Mitsubishi has developed technician training materials that are available on the company’s website, he says.

Technicians also should make sure the cabling size is adequate for the loads expected, Canfield says. “The cabling size will need to be increased any time an alternator with additional output is installed,” he says. “It’s like installing a water pump on a garden hose – you’re only going to get so much water through a hose of a given size.”

Alternate alternators
When the problem really is a worn-out alternator, what’s the best type of replacement part to buy? “Look at the total cost of maintenance when buying an alternator,” Karr says. An older, remanufactured brush-type alternator often is used for replacement because it’s the lowest-cost component, but the total cost of ownership will be higher because of the cost of downtime. “The enemies of an alternator are heat and vibration,” he says. “Brushless designs inherently handle these conditions better than brush-type alternators.”

Braga agrees that a brushless alternator lasts longer than a brush-type design under the same conditions. “Brush-type alternators tend to be less expensive, but have a shorter warranty period,” he says. “We believe most customers will benefit from an alternator that provides higher output at lower RPM,” especially considering the continuing trend to gearing engines for lower cruise RPM.

From a design standpoint, the biggest challenge with a brushless alternator is the low-end capability – the amount of power generated while the vehicle is idling, Canfield says. A built-in remote sense feature allows the alternator to measure voltage at the battery’s positive connection so that the battery will receive the proper voltage regardless of cable capacity or condition, he says.

Improving starter life
With so many of today’s trucks cranking up after an overnight shutdown, what can fleets do to improve starter life? “A system approach to the charge/start system is key,” Karr says. Batteries, wiring, starter and alternator all have to be given equal focus when diagnosing cranking issues, he says. “Does your shop already have a defined procedure and the equipment to troubleshoot this system?” Karr asks. “If not, you should consider purchasing one of the new battery/charge/start system analyzers on the market and train your technicians in proper use. Such a unit will pay for itself if it saves one misdiagnosis.”

To make an accurate diagnosis, according to Karr, technicians need to test the battery’s state of charge and cold cranking amps, the starter system’s main cable voltage drop and control function, the alternator cable’s voltage drop and regulator function, and the system’s output.

Fleets should check the condition of their batteries regularly and discard batteries that no longer take a charge or show physical wear to ensure the starter’s life expectancy, Braga says. “If the battery is deteriorating, the starter may not receive the correct cranking amps needed to crank the engine,” he says. Checking for proper cable connections to and from the starter and battery – as well as cleaning terminal connections and replacing old cables that are worn and create high resistance – can ensure correct starter life. “It also helps to ensure that the engine has no internal mechanical problems that would create unnecessary load during cranking,” Braga says.

Experts say technicians should understand that low voltage – whether caused by a bad battery, high-resistance cable or a bad connection – increases the amps drawn by the starter and risks overheating it. “Think of the starter as a single component within a complex system,” Canfield says. “It’s not unusual for starters to fail because the alternator is undersized.”

Low-voltage cutoffs and overcrank protection (OCP) – an integral thermal cutoff designed to protect the starter from overheating if it is allowed to crank for extended periods on a nonrespondent engine – are helpful, but these do not address the root cause, Canfield says. “Make sure the starter has sufficient output at idle to handle all the vehicle loads, plus 20 percent,” he says. “Then, spec a starter that will be powerful enough to crank the engine at the lowest temperature expected.” During the winter, the use of lower-viscosity oils approved for frigid conditions reduces both starter amperage draw and cranking time, Canfield says.

Whatever new vehicle specification or aftermarket starter or generator fleets choose, experts agree they also should purchase high-quality components and get their technicians up to speed on understanding the system as a whole and troubleshooting it properly – all of which will help keep their trucks on the road at a lower overall cost.