In many cases, soon after a new alternator has been installed, it is found to have failed prematurely. here i will try to highlight some of the probable causes of premature failure.

Here i have included illustrations of some common problems.

Because many of the new alternators are capable of charging at rates in excess of 110 Amps, the battery should be fully charged before use to avoid overheating the alternator by trying to use it as a battery charger.

Alternators are NOT battery chargers, they are battery maintainers as well as supplying current for vehicle amenities. Symptoms of this type of damage are a burnt stator.

In many newer vehicles, the alternator is located in an area that allows very little ventilation. The area around the rectifier on the back of the alternator plugs up with dirt and fibers, causing the unit to overheat.

Rear alternator bearing failure be caused by over tightening the belt or a seized belt tensioner. The bearing is retained in the alternator by either an aluminum ring or a plastic retainer, which under pressure, will collapse.

Drive belt slippage cause overheating and bearing damage. Thread damage on the rotor of the alternator is caused by improper pulley installation methods.

Cracked terminal insulators are caused by over tightening the terminal nuts. Improper changing of the alternator clock position may result in broken brushes and brush holders.

Drive Belt Tensioner too Tight Bearing Damage

Problem:

Picture #1 shows the drive plate on this alternator which has been scored by the fan.

This is caused by the belt tensioner not operating properly. The tensioner could be tight or possibly seized, which puts extreme tension on the drive end bearing, causing premature bearing failure.

This can also cause the rear bearing to fail. ( Refer to picture #2 )

Solution:

It is extremely important that the installer check the operation of the belt tensioner before installing any alternator. If it does not work properly, REPLACE IT.

Drive Belt Slippage

Problem:

These pictures show fan belt material on the front of the drive end plates of the alternators. This is caused by fan belt slippage.

Slippage of the belt can be caused by a loose or glazed belt, worn or misaligned pulley. Often this can be detected by a shiny or discolored pulley (Blue) or this black belt material. Pulleys can be misaligned with the other pulleys on the engine when the installer changes them from one alternator to another. The proper spacers must be used or removed as required.

Solution:

Often fan belts that appear to be tight may not start to slip until alternator is under full load. It is extremely important to inspect the old alternator and pulley before replacing them. If the belt is worn, glazed or cracked, REPLACE IT.

Make sure the belt tension is correct. Applications without automatic belt tensioners must be adjusted manually. Applications with automatic belt tensioners must be inspected to see if they operate correctly, if not, REPLACE THEM.

Rotor Threads Damaged

Problem:

The enlosed picture shows that the rotor threads on the alternator shaft have been damaged (Stipped).

This can be caused when replacing the pulley and starting the nut on the thread with an air impact, or using a hammer when removing the pulley.

Solution:

Start the pulley nut by hand initially to avoid possible cross threading of the shaft. Then tighten to spec with air impact.

Do not use a hammer directly on the shaft when removing the pulley.

Cracked Terminal Insulator

Problem:

Cracked battery insulator on the alternator caused by over tightening. (Often caused by air impact)

Solution:

It is extremely important that these connections are tightened with a wrench, by hand, and not an impact. The installer must use caution when manually tightening these nuts, not to give that last reef on the wrench.

Fan Belt Problems

 On many occasions, soon after installing a new fan belt, the vehicle throws the belt off or shreds the outer edges. Here are a few of the causes of this type of problem.

On V-belt systems, worn pulleys, improper pulley alignment, or damaged pulleys are usually the cause of frayed or broken belts. V-pulleys require the pulley to have smooth, machined surfaces to ensure good belt to pulley contact that will prevent belt slippage.

Improper alignment will cause belts to climb and jump off the pulleys. Pulleys can be damaged by rocks or improper installation, causing knife edges to be formed, which will cut the sides of a fan belt when passing over this damaged area.

Serpentine belts systems have developed a whole new set of problems for the technician. Idler pulley or alternator bearing failure is a major cause of new fan belts being destroyed soon after installation. Usually the belt has burnt areas and the belt grooves have a sooty material in them.

When the sides of a serpentine belt become frayed, or lose a groove or two of belt material, the cause is probably a worn idler pulley. Flat idler and tensioner pulleys wear in the center, resulting in the sides of the pulley become raised. It is this raised portion of the pulley that causes damage to the sides of the belt.