Alternators & Starters
Good news, Hot news.
Tom Berg
Equipment Editor
Sitting down to ponder the details of spec'ing a new truck? Don't forget the alternator. And since we're on the topic of alternators, we've got some good news and some hot news.
The good news is, they should last longer, thanks to pad mounting and a single serpentine belt now employed by some truck builders. The hot news is, they might die quicker because of higher heat under the hood.
The single-belt arrangement is like that used by auto and light-truck makers for about 15 years. One multi-groove belt wraps around all pulleys and is kept tight by a tensioning pulley. All accessories, including the alternator, sit on solid pads and their pulleys are lined up on a single plane.
You can't move them to tighten the belt and you don't need to, because the tensioning pulley takes care of that. When the belt wears out, it takes only a few minutes to move that pulley and change the belt, versus an hour or more to get at the second or third inside V-belt on traditional mounting systems. Also, there are no mounting "ears" on accessories to break, with four bolts securing each accessory to a sturdy pad.
Freightliner and International are among builders using the pad-and-serpentine-belt arrangement, according to our sources. Others may, also. It's something to look for — and ask for.
Meanwhile, the new cooled-EGR diesels run hotter, so heat trapped under the hood is greater. Testing by Leece-Neville shows it's up by 14 or more degrees Fahrenheit, exceeding 100 under some conditions.
The company has toughened its alternators with bigger diodes and more robust insulation and varnish on wiring and windings. It's also redesigned the internal fan to move more air. Other alternator makers, like Denso, say they've made similar changes in recent years.
Although alternators are now subject to higher heat, it's not so with batteries or starting motors. Batteries are outside the engine compartment and sometimes subject to freezing. Cranking motors are down low on the engine, where they get more external air flow.
The alternator is supposed to adjust its voltage-charging rate according to temperature. But it has no idea of ambient temperatures, so can send too much or too little voltage to the batteries. However, it will send the correct rate of charge if it's equipped with what engineers call "remote sense."
This is a simple small-gauge wire strung from a third post on the alternator to the battery box. It senses the batteries' temp and keeps the alternator's internal regulator informed. It can then adjust voltage to keep the battery charged — especially in cold weather — and cut voltage when it's hot outside to avoid cooking the batteries. Ask for remote sense when you order the alternator.
Starters are not hurt by the new, higher heat, but there's a trend toward "soft starting" that can affect the batteries and alternator. Soft starting turns the engagement gear more slowly, easing shock to the gear and the flywheel. But in so doing, the starter uses two to three times more amps than before. This means batteries must be kept healthy, especially in frigid temps.
On a lighter note, starters will soon be available with lighter-weight gear-reduction apparatus. The gear-and-shaft assembly now weighs 50 to 62 pounds on a typical starter; this will be cut to 42 pounds in new models about to be introduced. Look for 'em.
Once in service, alternators tend to fail at the most inopportune times — usually, when the vehicle is out on the road. You can avoid this with a recently introduced warning device designed by a pair of electrical engineers, Al Lesesky of Vehicle Enhancement Systems and Bruce Purkey of Purkey's Fleet Electrics.
Their Low Voltage Disconnect looks at the voltage produced by the alternator every 60 seconds and periodically compares it to what it should be making. If it senses undercharging, it disconnects non-essential loads (usually accessories in the sleeper), then warns the driver (or whoever else looks at a display panel) with fault codes. It warns of impending failure whether the alternator undercharges or overcharges. The warnings are available before the truck leaves home, so the alternator can be replaced on the owner's terms. The Low Voltage Disconnect is sold through Delco Remy distributors.
