Charging System Resistance Tests

Generator Terminals:

These tests will show the amount of voltage drop across the generator output wire from the generator output (B+) terminal to the battery positive post. They will also show the amount of voltage drop from the ground (-) terminal on the generator to the battery negative post.

A voltmeter with a 0 - 18 Volt DC scale should be used for these tests. By repositioning the voltmeter test leads, the point of high resistance (voltage drop) can easily be found.

Test points on the generator may be reached by either removing the air cleaner housing or below by raising the vehicle on a hoist.

Preparation
1. Before starting test, make sure battery is in good condition and is fully-charged. See Starting and Charging/Battery for more information.
2. Check condition of batter cables at battery. Clean if necessary.
3. Start the engine and allow it to reach normal operating temperature.
4. Shut engine off.
5. Connect an engine tachometer.
6. Fully engage the parking brake.

Test
1. Start engine.
2. Place heater blower in high position.
3. Turn on headlamps and place in high-beam position.
4. Turn vehicle interior lamps on.
5. Start engine. Bring engine speed up to 2400 rpm and hold.
6. Testing (- ground) circuitry:

Battery Voltage Test:

a. Touch the negative lead of voltmeter directly to battery positive POST.
b. Touch the positive lead of voltmeter to the B+ output terminal stud on the generator (not the terminal mounting nut). Voltage should be no higher than 0.6 Volts. If voltage is higher than 0.6 Volts, touch test lead to terminal mounting stud nut and then to the wiring connector. If voltage is now below 0.6 Volts, look for dirty, loose or poor connection at this point. A voltage drop test may be performed at each (- ground) connection in this circuit to locate the excessive resistance.

7. Testing (+ positive) circuitry:
a. Touch the positive lead of voltmeter directly to battery negative POST.
b. Touch the negative lead of voltmeter to the ground terminal stud on the generator case (not the terminal mounting nut). Voltage should be no higher than 0.3 Volts. If voltage is higher than 0.3 Volts, touch test lead to terminal mounting stud nut and then to the wiring connector. If voltage is now below 0.3 Volts, look for dirty, loose or poor connection at this point. A voltage drop test may be performed at each (+ positive) connection in this circuit to locate the excessive resistance. This test can also be performed between the generator case and the engine. If test voltage is higher than 0.3 Volts, check for corrosion at generator mounting points or loose generator mounting.