With the voltmeter turned on and set to measure the voltage of a 12-volt battery, you should see a voltage reading for the battery in the area of 12.5 to 12.8 volts.3. Unhook the voltmeter from the battery and start your vehicle.
The battery will eventually drain and the engine won't have enough energy to turn over. There are some basic troubleshooting techniques for checking your alternator.
Instructions
Test the Voltage Output
1. Turn your vehicle and all of its accessories off. Open the hood and access the battery. Depending on the year, make and model of your car, you may need to remove various guards or shields to access the terminals of the battery. You may need small wrenches or screwdriver to remove the guards.
2. Hook the negative and positive leads/clamps of a voltmeter to the negative and positive terminals on the car battery.
A digital voltmeter Testament prove indispensable when troubleshooting your alternator.The alternator in your vehicle is designed to convert the mechanical energy provided by the engine into electrical energy. This electrical energy is used to sustain the vehicle's battery, as well as to provide extra power to run the accessories, such as lights, stereos or other optional equipment. If your alternator isn't working as it should, the vehicle is in trouble.While the vehicle is running, reconnect the voltmeter to the battery. With the engine idling, you should see a voltage output approximately 1.5 to Two volts above your previous reading. The exact voltage will vary, but if you do not see an increase or the increase is above Three volts, you may have a faulty alternator.
Test the Load
4. Start the engine and connect the voltmeter's positive and negative leads to the battery. Turn on the headlights and switch them to the high-beam setting. Check the voltmeter. With the high beams on, you should see a reading in the area of 13.8 to 14.2 or 14.5 volts.
5. Put the vehicle in "Park" and set the emergency brake. Have your helper get behind the wheel and press on the accelerator so that the engine revs to approximately 1,500 RPM. You should now note a voltmeter reading of approximately 14.2 to 14.6 volts. A reading of less than 14.2 volts may indicate a faulty diode within the alternator.
6. Tell your helper to turn off the headlights while maintaining the vehicle's rpms at 1,500 for approximately one minute. Watch the voltmeter. If the alternator and voltage regulator within the alternator are working correctly, the reading should not be above 14.8 volts.
