The modern commercial diesel engine relies on precise, reliable flows of fuel, air and coolant to do its job. What you don’t want flowing through your engine, however, is stray electrical current that can quickly destroy internal components and wreak havoc on sophisticated electronics.

These stray amps are coming from computer-controlled direct injection to driver-assist platforms—not to mention all the bells and whistles in today’s driver-friendly cabs. These assets absolutely require a high-amperage/high-output power supply.

In some cases, this power originates from a case-ground alternator. This means the alternator’s housing is part of the electrical circuit between the alternator and battery. Because the alternator housing is mounted to the engine, this arrangement provides a clear path for current to do a variety of rather nasty things. As alternators spend more time operating under high-load conditions, conventional grounds are easily overtaxed, potentially dispatching current where you don’t want it to go.

Additionally, increased alternator output typically means greater electrical noise, which can mess with onboard electronics to the point of triggering false trouble codes. Pity the shop technician (and his or her boss) who spends precious hours tracing the root cause of a non-existent problem.

Major alternator manufacturers have addressed this issue through the development of Isolated Ground Technology, which provides a dedicated electrical path between the alternator and battery. Rather than grounding to the alternator case, these units provide a closed-loop circuit that keeps your current where it belongs.

For example, Leece-Neville IdlePro and IdlePro Extreme alternators feature a return cable from the battery that is grounded to an electrically insulated, thermally conductive internal membrane. The result: a significantly reduced noise signature and elimination of stray current moving through your vehicle’s priciest metal.

Here’s the moral of the story: Think about more than the output and efficiency rating when choosing an alternator. Based on the content, value and vintage of your asset, you might be best served by a unit offering Isolated Ground Technology to avoid potentially costly repairs and diagnostic headaches.

This article was contributed by Clive Harley, vice president of engineering for Prestolite Electric.