TROUBLE SHOOTING
Note. See TROUBLE SHOOTING article in GENERAL INFORMATION.
VOLTAGE DROP TEST
Connect voltmeter positive lead to terminal "B" at generator and negative lead to positive battery post. Ensure that voltmeter leads are clear of all moving components. Start engine. Turn on blower motor and headlights. If voltage reading is .2 volt or less, output wire is okay at this time. If voltage reading is greater than .2 volt, repair output wire or fusible link between generator and battery.
GENERATOR OUTPUT TEST
Note. If battery is fully charged, disable ignition system. Crank engine for about 15 seconds to partially discharge battery.
- Ensure generator belt tension is correct. Turn ignition off. Disconnect battery negative cable. Disconnect output wire from terminal "B" of generator. Securely connect test equipment as shown. (Scheme 6) Attach engine tachometer, and connect battery negative cable.
- If voltmeter indicates battery voltage, go to next step. If voltmeter indicates zero volts, check for open wire between positive battery terminal and generator terminal "B", blown fusible link, or poor ground.
- Start engine. Turn headlights on high beam, and operate blower motor at high speed. Quickly increase engine speed to 2500 RPM, and observe maximum current readout on ammeter. Ammeter reading should not be less than minimum output amperage. See «GENERATOR OUTPUT SPECIFICATIONS»(ref-4076-S40130310792000061200000) table. If generator output is not as specified, remove and bench test generator.
| Application | Minimum Output Amperage |
|---|---|
| 75-Amp Generator | 52.5 |
| 90-Amp Generator | 63 |
GENERATOR OUTPUT SPECIFICATIONS
Scheme 6
REGULATED VOLTAGE TEST
- Ensure battery is fully charged and generator belt tension is correct. Turn ignition off. Disconnect battery negative cable. Disconnect output wire from terminal "B" of generator. Securely connect test equipment as shown. (Scheme 7) Attach engine tachometer, and connect battery negative cable.
- Turn ignition on. If voltmeter indicates battery voltage, go to next step. If voltmeter indicates zero volts, check for open wire between positive battery terminal and generator terminal "S", blown fusible link, or poor ground.
- Start engine. Operate engine at about 2500 RPM with all lights and accessories off. When generator output drops to 10 amps (ammeter reading) or less, note voltage output on voltmeter. Ensure voltage is as specified. See «REGULATOR VOLTAGE SPECIFICATIONS»(ref-4076-S17552180902000061200000) table. If voltage is not as specified, test generator and related wiring. If generator and related wiring are okay, replace voltage regulator.
| Ambient Temperature °F (°C) | Volts |
|---|---|
| 4 (-20) | 14.2-15.4 |
| 68 (20) | 13.9-14.9 |
| 140 (60) | 13.4-14.6 |
| 176 (80) | 13.4-14.5 |
REGULATOR VOLTAGE SPECIFICATIONS
Scheme 7
Positive Diode Test
Using ohmmeter, check continuity between each positive diode and stator coil lead terminal, in both directions. See STEP 1 in illustration. (Scheme 8)or (Scheme 9). Continuity should exist in only one direction. If continuity of any positive diode is not as specified, replace rectifier assembly.
Negative Diode Test
Using ohmmeter, check continuity between each negative diode and stator coil lead terminal, in both directions. See STEP 2 in illustration. (Scheme 8)or (Scheme 9). Continuity should exist in only one direction. If continuity of any negative diode is not as specified, replace rectifier assembly.
Diode Test
Using ohmmeter, check continuity of each diode, in both directions. See STEP 3 in illustration. (Scheme 8)or (Scheme 9). Continuity should exist in only one direction. If continuity of any diode is not as specified, replace rectifier assembly.
