Connect charging system test equipment following manufacturer's instructions. Check charging system output voltage at 2000 RPM. See GENERATOR OUTPUT SPECIFICATIONS table. If output voltage is high, replace voltage regulator and retest. If output voltage is low, go to next step. If output voltage is correct, go to step 3.
If output voltage is low, by-pass regulator (full field generator) by grounding terminal "F" at back of generator. See Fig 1 or Fig 2 . Recheck charging system output voltage. See GENERATOR OUTPUT SPECIFICATIONS table. If output voltage is high, replace voltage regulator and recheck. If output voltage remains low, repair or replace generator.
With engine at 2000 RPM, place heater blower switch on highest setting and turn on headlights (high beam). Ammeter reading should be 30 amps or more. If amperage output is less than 30 amps, repair or replace generator.

GENERATOR OUTPUT SPECIFICATIONS

Application

Amps

Volts

ES300, GS300, GS430 & IS300

10 Or Less

13.2-14.8

LS430

10 Or Less

⁽¹⁾ 13.7-14.8

RX300

LB3 Type

10 Or Less

13.5-15.1

SC1 Type

10 Or Less

13.2-14.0

⁽¹⁾	Measured at 77°F (25°C) and 2000 RPM.

Fig 1: Full Fielding Generator (ES300 & RX300)

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Except LS430