Alternator Output

Connect charging system test equipment as described in manufacturer's instructions. Check charging system output voltage at 2000 RPM. 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). See ALTERNATOR OUTPUT SPECIFICATIONS table.
If output voltage is low, by-pass regulator (full field alternator) by grounding terminal "F" at back of alternator. See Fig 1, Fig 2 or Fig 3 . Recheck charging system output voltage. If voltage now exceeds output voltage specified in ALTERNATOR OUTPUT SPECIFICATIONS table, replace regulator and recheck. If output voltage is still incorrect, repair or replace alternator.
With engine at 2000 RPM, place the heater blower switch on highest setting and turn on headlights (high beam). Ammeter reading should be 30 amps or more. If amperage output is incorrect, repair or replace alternator.

ALTERNATOR OUTPUT SPECIFICATIONS - @ 2000 RPM ⁽¹⁾

Application

Amps

Volts

ES300

10 Or Less

14.0-15.0

GS300

10 Or Less

13.6-14.8

LS400

10 Or Less

13.7-14.7

SC300 & SC400

10 Or Less

13.9-15.1

⁽¹⁾	Measured at 77°F (25°C).

Fig 1: Full Fielding Alternator (ES300)

Fig 2: Full Fielding Alternator (LS400)

Fig 3: Full Fielding Alternator (Typical)