Delco alternators have replaced most Delco generators, as they are generally maintenance-free and produce higher electrical output -- necessary for powering the electrical equipment in today's vehicles. When generators were fitted in the past, most vehicle wiring was "positive ground," meaning the cable from the positive battery terminal connects to the vehicle's metal body. Around the same time as alternators were introduced, however, vehicle manufacturers commenced "negative ground" wiring, meaning the cable from the negative battery terminal connects to the vehicle's metal body. Fortunately, the procedure for testing a 6 volt positive ground Delco generator is no different than that for testing a negative ground Delco alternator.
Access your vehicle's battery so you can test the 6 volt Delco generator. It's usually under the hood, but is sometimes in the trunk, depending on the model of your vehicle.
Tuck any loose clothing out of the way of the engine. Turn on the vehicle's engine and let it run at idle speed. Idle speed is sufficient for a Delco generator to produce 6 volts.
Use a voltmeter to test the output voltage from the Delco generator. The voltmeter has two wires: one red and one black, indicating positive and negative, respectively. On the ends are metals sensors; place these on the positive and negative battery terminals.
Put the red wire sensor directly onto the positive battery terminal labeled "Pos." Put the black wire sensor onto the negative battery terminal labeled "Neg."
Check the measurement from the voltmeter display. It will read 6 volts if the Delco generator is operating correctly. It is unlikely to exceed 6 volts when the engine is at idle speed, but if the reading is considerably lower than 6 volts (below 4) then the generator isn't producing the correct voltage and needs checking. However, first complete the next test.
Get a helper to sit in your vehicle. Ask them to increase the engine revs to about 2,000 RPM. This increases the generator rotation speed, increasing the voltage output. However, the vehicle is also fitted with a voltage regulator that automatically limits the voltage to 6 volts.
Repeat the test using the voltmeter. The reading should be 6 volts if the Delco generator and voltage regulator are operating correctly. If the voltage is below 6 volts you need to get the generator checked out by a professional. If the voltage is more than 10 to 15 percent higher than 6 volts then the voltage regulator is not working properly. Continued use of your vehicle may damage the electrical equipment and blow the fuses, so get it checked as soon as possible.
