1. Never, ever remove your negative (or positive) battery cable while the car is idling to see if it stalls, as a test for your alternator. This causes a major power surge that can fry anything in its path, including the voltage regulator, diodes, and even possibly the vehicles onboard computer. A cheapo voltmeter can cost as little as $9.00. Do the math.
2. To see if a vehicle is charging or not, put the voltmeter on the battery with the car not running. It should read 12 to 13vdc depending on the state of charge of the battery. Turn all accessories off. Start the car. The voltmeter should read 14 to 15vdc. If so, charging system is ok. If voltage does not increase, charging system is faulty. UPDATE: On newer vehicles with later design voltage control, it may be necessary to observe voltage for 30sec to 1 min, turn headlamps on and watch for voltage increase.
3. The most important part of alternator installation AND diagnosis is bringing the battery to a full state of charge. An excellent opportunity to do this, is during the repair process. Huge mistakes are common by the installer, as to whether this step can be bypassed. The most common mistake by the average person is thinking :
a. ” The battery must still be charged up, it still cranks the car over.” (WRONG)
b. “The battery doesn’t need charged, my headlights are still nice and bright.” (WRONG!)
c. “ I shouldn’t have to charge the battery, I only drove it for a little ways with the alternator not charging.” (WRONG!!)
d. “The battery doesn’t need charged, it’s brand new.” (WRONG!!!)(WRONG!!!)(WRONG!!!)
These statements are all false. It is the author’s strong opinion that charging the battery at a low rate for minimum of 2 hrs. is under any and all circumstances absolutely necessary. If a battery has been severely discharged, a charging period of 12-24 hrs. at the lowest amp setting may be necessary.
CHARGING A BATTERY IS LIKE WASHING YOUR CAR. YOU PUT THE SOAP IN THE BUCKET, THEN TURN THE HOSE ON FULL BLAST AND THE BUCKET GETS FULL TOO FAST. YOU GET A BUCKET FULL OF FOAM AND TEN MINUTES LATER THE SUDS BREAK UP AND YOU DON’T HAVE ANYTHING. YOU HAVE TO ADD THE WATER SLOWLY TO OBTAIN A FULL BUCKET. SAME THING WITH A BATTERY CHARGER, WHEN YOU CHARGE A BATTERY AT A HIGH AMPERAGE RATE, THE CHARGE GOES IN ONLY ON THE TOP SURFACE OF THE CELLS. THEN TEN MINUTES LATER, IT’S LIKE YOU NEVER DID IT. THE ONLY WAY TO COMPLETELY CHARGE A BATTERY IS AT A LOW AMPERAGE RATE, FOR A LONG PERIOD OF TIME, SO IT IS ABSORBED FROM BOTTOM TO TOP SLOWLY.
Don’t have a charger ? Be smart. Take the battery out of the vehicle and take it to your local part store or mass market retailer. Most of them will be happy to “charge and check” for a nominal fee, or for free on the chance of selling you a new battery. If the battery is over 3 years old, this is a good time to think about buying a new battery. If the battery is over 4 years old, think really, really hard. The average life expectancy of a properly rebuilt alternator that is properly installed is 3-4 years. The average life expectancy of a properly rebuilt alternator installed on a low or failing battery is 3-4 months. Once again: Do the math. The normal course of events is: as the battery goes through a failure period, the alternator suffers intense abuse. Most people never know their battery is failing because it still starts the car. Unfortunately, newer cars with the advent of computerized fuel injection will start on 100 amps with little or no crank time. A 500 CCA battery could loose half it’s cells and still deliver a start. The driver never knows the alternator is working overtime to keep the failing battery up to par.
THINK OF YOUR CHARGING SYSTEM THE WAY A TEETER -TOTTER WORKS. THE ALTERNATOR IS ON ONE SIDE OF THE BOARD. THE BATTERY IS ON THE OTHER. THE VARIOUS ELECTRICAL ACCESSORIES YOU TURN ON WOULD BE THE FULCRUM. AS THE BATTERY BECOMES WEAKER AND OLDER, IT WOULD WEIGH MORE AND MORE, SHIFTING THE WEIGHT LOAD MORE AND MORE ON THE ALTERNATOR. THE ALTERNATOR NEVER GETS A CHANCE TO REST AND CONSEQUENTLY RUNS AT HOTTER TEMPERATURES IN ORDER TO MAINTAIN A BALANCED VOLTAGE.