Generating and Starting

What’s the difference between a ‘rebuilt’ starter or generator and a ‘remanufactured unit?  Is one really that much better than the other?



An alternator is an amazingly robust component that must operate tirelessly over an extremely wide range of temperatures and rpm ranges in order to keep a vehicle moving.  These units take advantage of “induction,” a term describing the fact that when copper windings sweep through a magnetic field, electrons begin to flow in those windings.   Today’s alternator typically produces more than a hundred amps, and consists of a cast aluminum case with a spinning magnetized core called a rotor that can reach speeds of up to 14,000 rpm. It spins its magnetic field through the stationary outer winding called a ‘stator,’ and that’s where the alternating current that gave this component its name is created.  The alternating current is rectified and thus converted to DC current by a series of diodes wired to tips of the stator winding and the output of the alternator is constantly and consistently controlled by logic circuits in an electronic regulator or by the PCM by way of the brushes.

The once-external alternator cooling fan has been modified and moved inside the case on just about all alternators built over the past two decades (some have two fans) due to space limitations and higher under hood temperatures.  Chrysler was on the cutting edge with the internal fan concept, having built their chargers that way for years before most of the rest of the industry caught on.

Late model diesel pickups (some Ford 6.0L applications, for example) are fitted with not one, but two small but very powerful alternators now instead of one large one, once again due to extreme demand and space limitations.  Two 150 amp alternators can produce a collective 300 amps, and it would take a large and very expensive charging unit to do that same job using only one.

With all that an alternator goes through in today’s tightly packed superheated engine compartments, it’s somewhat surprising that they last as long as they do!



Starters capitalize on magnetism that is created by current flow instead of the other way around like alternators, and while the current that makes the unit work still flows through brushes, starter brushes slide across a commutator composed of coppers strips wired to armature segments, and old time field coils have been replaced by ceramic magnets.  Due to space restrictions, today’s armatures are smaller and spin a lot faster than the starters of yesteryear, and the necessary power to spin the engine is delivered through reduction gearing internal to the starter. Today’s starters are crisp, tough, fast, and powerful, but they’re not quite as robust as the starters of bygone years, because they don’t have to be.  A fuel injected engine doesn’t generally need as much spinning during its lifetime as a carbureted engine.  Oddly, a ten year old low mileage car may wear its starter out almost as quickly as a ten year old high mileage car because the starter doesn’t care about highway miles or age, it only cares about the number of engine starts it has had to accomplish.


A Link That Needs to be Strong

Every wrench twister has replaced more than a few alternators, and a somewhat smaller group has repaired at least one.   Brushes, regulators, bearings, and rectifiers are fairly easy to replace on most older alternators, but due to rectifier connections on new units that are soldered rather than plugged or lugged, repairs are somewhat harder on newer ones and individual component parts have become almost impossible for the average technician to obtain.  It makes more sense to replace the whole unit.  Since the alternator is such a critical link to the dependability of a vehicle, and since some alternators can be so tough to replace, choosing the right replacement unit is a no-brainer.

Temperature spikes raise the resistance of the windings and negatively affect the output, and late model alternators must be repaired with that clearly in focus.  A 100,000 mile alternator that has been through year after year of summer and winter and seedtime and harvest needs a lot more than brushes and bearings if it is to consistently perform.  In many if not most cases,’ rebuilt’ alternators come with high failure rates (I heard one parts counterman quote a figure as high as 50 percent), so a truly ‘remanufactured’ unit is the wisest choice.  And with all the legal loopholes available to the box labelers, it’s best to go with alternators and starters produced by tried and proven remanufacturers like Visteon.


So What’s the Difference?

‘Rebuilders’ generally disassemble the alternator or starter, bead blast the case, do a cursory physical and electrical inspection of the parts, reassemble the unit with new bearings, brushes, and regulator, and bench test before boxing it up as inventory. Starters may or may not be painted. The above operations are done with varying degrees of detail, and without pointing fingers, we all know money talks:  Profit margins are important, so the more units they can build without replacing all the guts, the better the bottom line looks.   The wrinkle is that one alternator looks pretty much like any other one to the untrained eye, and the price of a rebuilt may or may not be a less than a truly remanufactured unit.

Remanufacturers take a much deeper approach.  At Visteon, OEM specifications are followed as carefully and as completely as possible during the reman process.  Each new remanufacturing process is rigorously tested by putting sample units through rigorous 1000 hour test periods to analyze weaknesses and failures.  OEM alternators which are failure prone receive special attention in that their weak areas areas are strengthened to make the remanufactured alternators more reliable than some of the more failure-prone OEM chargers.

In  the remanufacturing process used by Visteon, each separate component has to meet certain minimum standards. Rotors and stators are carefully and comprehensively checked for radial runout and/or out-of-round conditions as applicable.  Rotor slip rings are not only measured for runout, but also for diameter and finish. Why check the diameter?  Because a slip ring that has wear may be too thin to last.  It’s easy to understand why the slip rings would be checked for out-of-round conditions, but why check the finish?  Those of us who have repaired alternators have sanded the slip rings and felt like we were doing a good thing, but finish is important because the marriage of the brushes with the surface of the slip rings is critical; slip rings that are even slightly too rough may generate sparks that cause radio interference, and if that weren’t enough of a problem, those same little sparks can send a continual fusillade of voltage spikes back into the delicate innards of the electronic regulator or PCM, and we all know where that can lead.  The rotor and stator, if they are to be reused, are juiced up with thousands of volts to check for chinks in the insulation, and if a rotor or stator fails, a carefully chosen outside vendor replaces the defective winding on the component(s) in question.

Premature field failures of Visteon remanufactured units are tracked by lot number to the place on the line where the parts were tested and assembled, and changes are made as necessary to correct the concern.



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