AS MOTORISTS, how much do know about the charging system? Is it that important to your vehicle's overall performance?

Well, the charging system consists of the alternator, regulator and the battery.

"The alternator provides electricity that charges the battery and operates electrical components. A regulator adjusts alternator output to the demand placed on the alternator by electric components," explains Keith Austin, an experienced auto-electrician with over 30 years in the motoring business.

According to Austin, the alternator prevents excessive electric output, which can cause serious damage to the vehicle. It must be noted that in some motor vehicles, the regulator and the alternator are placed separately, while in others, the two are integrated, with the regulator housed in the alternator.

When there is a charging-system problem, how do you know? What are the signs?

A charging-system problem makes itself apparent in one of four ways, Austin points out.

No charge - With the engine running, the charging system light glows, or the ammeter registers zero, or shows a slight discharge.

Discharge - With the engine running, the charging-system indicator light glows or the ammeter shows a significant discharge.

Undercharge battery - With the engine running, the charging-system indicator light may glow dimly, or the ammeter may show a slight discharge when accessories are on. The headlights will be dim.

Overcharged battery - With the engine running, the ammeter will show a high charge, even with all lights and accessories on. The battery will need water quite often and headlights will be very bright. The bulbs and fuses may burn out frequently.

Testing the alternator And regulator

Step 1: Connect a voltmeter to the battery and make note of the battery voltage with the engine off. If the voltage is less than 9.6 volts, charge battery and take another reading.

Step 2: Start and run the engine at 1500 to 200 rpm. Record the voltage reading. The reading with the engine running should be two or more volts higher than the battery voltage without the engine running. If it is, the alternator is probably all right. If the voltage is not higher, take note of the servicing procedure below.

To check the regulator, continue to run the engine at 1,500 to 2,000 rpm until the voltmeter records the highest reading it will reach. If the voltmeter needle continues to climb, the regulator is faulty and should be replaced.

Servicing procedure

Check the alternator drive belt for damage.

Test the alternator drive belt for proper adjustment.

Inspect all connections at the alternator, regulator and battery for tight terminals and cleanliness. Carefully clean corrosion from terminals and see that the wires are not cracked or frayed. Replace damaged wires.

If the cause of the low-voltage reading has not been found, the alternator should be replaced or overhauled. To make sure, test the alternator for output. This is done by hooking up a voltmeter and disconnecting the alternator field terminal as the engine is run at fast idle. If the voltmeter does not read between 14 volts and 15.5 volts, the alternator should be removed from the car for servicing.

- P. M.