CAUTION: Carbon pile testing is part of this procedure. To avoid battery explosion, turn carbon pile OFF before connecting to or disconnecting from test stand battery.

Mount generator on test stand. Set test stand controls to turn generator clockwise. Ensure ground polarity of generator and battery are the same. Ensure battery is fully charged. Connect voltmeter, ammeter and carbon pile (in the OFF position). Connect a 30-500 ohm resistor between battery and terminal "L" of generator. See Fig 1.
Slowly increase generator speed while observing voltmeter. If output is uncontrolled and increases to greater than 16 volts, rotor field coil is shorted and/or regulator is defective. A shorted rotor field coil can cause regulator failure. Replace or repair generator.
If voltage is less than 16 volts, increase speed and adjust carbon pile to obtain maximum generator output. Maintain voltage greater than 13 volts. If amp output is within 15 amps of rated output, generator is okay. If amp output is not within 15 amps of rated output, replace or repair generator. See GENERATOR USAGE/AMP OUTPUT RATING table.

Fig 1: Testing Generator Output (Caprice, Impala SS & Roadmaster)

Courtesy of GENERAL MOTORS CORP.

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

Generator Output Test

Use the Manual With the Right Hardware

When to See a Mechanic

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