Alternator 911

We’ve all done it. A quick charging system check to confirm the “no output” diagnosis, followed by a knuckle-skinning “re and re” of the alternator to produce…no output. What happened? A defect in the part is a natural assumption, but is it really likely? In fact, it’s more probable that the unit failed at startup. Correct installation can save many units and dramatically reduce costly comebacks.

According to Fred Padgett, Product Manager, Rotating Electrical Products for Robert Bosch Corporation, there are several points to remember when installing reman alternators:

Don’t use an alternator to recharge a discharged battery.

When installing an alternator, the battery should be fully recharged before vehicle use. In many cases, depending upon how thoroughly discharged the battery is, it can take 4 to 8 hours. Many technicians and DIYers don’t want to wait that long. In some cases with weather extremes the battery never gets fully charged and in all cases the alternator is being overly stressed asking it to do a job it was not designed to do, which leads to premature failure.

Check battery cables and connections.

Installers often stop at cleaning the corrosion off a visibly corroded battery terminal or battery cable connection, but to do a thorough job, voltage drop tests should be preformed between the battery cable terminal at the battery, and the opposite end of the same cable, whether it is at the starter, alternator, or a ground connection.

If the cables are not in good condition, the current produced by the alternator cannot adequately get to the battery to maintain the charge, and the alternator ends up working overtime just to attempt to charge the battery.

Alternator type-specific problems

Ford alternators from 1984 through 1994–Ford IAR alternators utilized a unique B+ connection. Instead of a threaded stud connection on the back of the alternator similar to most alternators, these units used a three-spade plug connector. Due to the high heat created by these alternators, these plugs and the wires leading to them break down over time. Any time a Ford IAR alternator is replaced, the plug connection on the end of the vehicle’s wiring harness should be replaced at the same time.

Voltage regulator functions

Depending upon the type of alternator being replaced, the functions in the alternator’s regulators are different, and can cause installers headaches, if the battery is not properly charged prior to installation.

Ford IAR Alternators – The voltage regulators in these units do not have “low voltage” protection, meaning that if the vehicle will start and the battery voltage is less than 12 volts, the alternator will do its best to recharge the battery. If a battery is extremely low or has trouble maintaining a charge, the IAR alternator will produce its maximum output attempting to charge the battery. In extreme cases the IAR can destroy its stator windings in as little as 10-15 minutes of running time, leading to a shorted or dead alternator.

GM CS 130 Alternators (as used on a majority of GM produced vehicles between 1985 and 1995) – These alternators do have “low voltage protection,” which can cause another problem. In essence, if the battery is too low, the voltage regulator senses battery condition and will not allow the alternator to “turn on” and attempt to charge a dead battery.

Soft start functions

Many alternators, including GM and Honda, incorporate a soft start function, meaning that the alternator does not start to charge until a load is placed upon the system — headlights, certain engine RPM etc. Many installers, not knowing the intricacies of the particular system they are working on, believe the product is no good because they do not see it charging as soon as they install it and fire up the engine.

Installation procedures

Due to the changes in design by some OE manufacturers from how the vehicles’ original components were made and how the same OEM’s aftermarket replacement components are made, strict adherence to installation procedures need to be followed. In the case of GM “CS” series alternators, for instance, the manufacturer of the voltage regulator changed the internal circuitry to be longer lasting and more resistant to heat. But in the process, the manufacturer made them more vulnerable to voltage spikes.

If the proper procedures are not followed and a voltage spike occurs during the installation, The voltage regulator gets “zapped” and thus the alternator appears to be no good.

And one more point: If the alternator you are replacing is equipped with an integral voltage regulator, make sure the remanufactured alternator includes a brand new, not reclaimed, integral voltage regulator.

Do reman alternators fail early? According to Bosch’s Fred Padgett, “Remanufactured alternators from a quality supplier perform just as well as the unit they are replacing.”