Alternator: Testing and Inspection

CAUTION:
- Do not mistake polarities of IG terminal and L terminal.
- Do not create a short circuit between IG and L terminals. Always connect these terminals through a lamp.
- Do not connect any load between L and E.
- When connecting a charger or a booster battery to vehicle battery, refer to battery charging.

Trouble in charging system will show up as one or more of following
conditions:
1. Faulty indicator lamp operation.
2. An undercharged battery as evidenced by slow cranking or indicator dark.
3. An overcharged battery as evidenced by excessive spewing of electrolyte from vents.
Noise from generator may be caused by a loose drive pulley, loose mounting bolts, worn or dirty bearings, defective diode, or defective stator.




FAULTY INDICATOR LAMP OPERATION




UNDERCHARGED BATTERY

This condition, as evidenced by slow cranking or indicator clear with red dot can be caused by one or more of the following conditions even though indicator lamp may be operating normal. Following procedure also applies to cars with voltmeter and ammeter.
1. Make sure that undercharged condition has not been caused by accessories left on for extended period of time.
2. Check drive belt for proper tension.
3. If battery defect is suspected, refer to BATTERY.
4. Inspect wiring for defects. Check all connections for tightness and cleanliness, battery cable connections at battery, starting motor and ignition ground cable.
5. Connect voltmeter and ammeter as shown .

Voltmeter
Set between generator B terminal and ground.

Ammeter
Set between generator B terminal and battery (+) terminal.

NOTE: Use fully charged battery.

6. Measure current and voltage.




No-load Check
Run engine from idling up to 2,000 rpm and read meters.

NOTE: Turn off switches of all accessories (wiper, heater etc.).

Standard current: 10 A maximum
Standard voltage: 14.1 - 15.2 V (at 20 °C, 68 °F)

NOTE: Consideration should be taken that voltage will differ somewhat with regulator case temperature as shown.

Higher Voltage
If voltage is higher than standard value, check ground of brushes.
It brushes are not grounded, replace IC regulator.




Lower Voltage
If voltage is lower than standard value, proceed to following check.

Ground F terminal and start engine, then measure voltage at B terminal as shown in left figure.
- Voltage is higher than standard value
It is considered that generator itself is good but IC regulator has been damaged, replace IC regulator.
- Voltage is lower than standard value
Generator itself has problem, check the generator.

Load Check
1. Run engine at 2,000 rpm and turn on head light and heater motor.
2. Measure current and if it is less than 30 A repair or replace generator.




OVERCHARGED BATTERY
1. To determine battery condition, refer to BATTERY.
2. If obvious overcharge condition exists as evidenced by excessive spewing of electrolyte, measure generator B terminal voltage at engine 2000 rpm.
3. If measured voltage is higher than upper limit value, proceed to disassembly of generator service.
4. Check ground of brushes. If brushes are not grounded, replace IC regulator. Then check field coil for grounds and shorts.