Generators & Regulators: Testing: Notes
- Perform generator system test. Replace generator if it fails that test. If it passes test, perform on-vehicle output check which follows. See Fig 1
.CAUTION: Always check generator for output before assuming that a grounded "L" terminal circuit has damaged regulator.
- Attach a digital multimeter, an ammeter, and a carbon pile load to vehicle.CAUTION: Be sure vehicle battery is fully charged, and carbon pile load is turned off.
- With ignition switch in OFF position, check and record battery voltage. Remove harness connector from generator. Turn ignition switch to RUN position with engine not running. Use a digital multimeter to check for voltage in harness connector "L" terminal.
- The reading should be near specified battery voltage of 12 volts. If voltage is too low, check indicator "L" terminal circuits for open and grounded circuits causing voltage loss. Correct any open wires, terminal connections. etc., as necessary. Attach generator harness connector. Run engine at a moderate idle, and measure voltage across battery terminals. If reading is over 16 volts or below previous reading, replace generator.
- Run engine at a moderate idle, and measure generator amperage output. Turn on carbon pile, and adjust it to obtain maximum amps while maintaining battery voltage above 13 volts. If reading is within 15 amps of generator's rating noted on generator, generator is good. If not, replace generator.
- With generator operating at maximum output, measure voltage between generator housing and battery negative terminal. Voltage drop should be .5 volt or less. If voltage drop is more than 0.5 volt, check ground path from generator housing to negative battery cable. Check, clean, tighten, and recheck all ground connections.