How to Use a Rectifier Regulator Tester

Alternators like these produce AC power that must be converted to DC power for on-board circuits.

For automobiles and motorcycles the battery is used to help start the engine. Once the engine has been started, it turns an alternator that generates electricity. However, this is AC (alternating current) power. The battery which needs recharging by the alternator is designed for DC (direct current). The ignition system, tail lamps, brake lamps, turn signals and gauges also need electric power to function. They are also DC components. To address this need for DC power, a regulator rectifier converts the AC power from the alternator to the necessary DC power. When the charging system isn't working properly, this is a component to check.

Things You'll Need

• Regulator rectifier
• Documentation for regulator rectifier
• Rectifier regulator tester

Instructions

1. Review the documentation for the regulator rectifier. Make sure you understand each pin connection. Depending upon the design, you will find at least one output lead. You will also find a negative pin that serves as the DC circuit ground.

2. Disconnect the rectifier regulator outputs. Keep it connected to the alternator. The output end is what you want to disconnect to test the output.

3. Connect the regulator rectifier tester. Insert the probe leads into the output voltage side and the ground. If you have multiple outputs, you will have to return to this point to test all other outputs. You may also touch a test lead to the vehicle chassis for a sufficient ground.

4. Start the engine. Do this for only a brief period of time to test the output. While you are conducting this test, the battery is providing power for all the on-board electrical systems. Since that means this test drains the battery, keep the engine on for less than one minute.

5. Test the regulator rectifier. Read the output indicator from the tester. Compare the results against what you should see. If you have multiple voltage outputs, test each of the remaining ones in the same manner. Just make sure you only run the engine briefly.

6. Determine the disposition of the regulator rectifier. If all of the outputs have checked out as good, then there is no need to replace the regulator rectifier. However, if even just one of the rectifier outputs is bad, the whole component must be replaced according to the directions stated in a repair manual.

Tips & Warnings

• Instead of using a regulator rectifier tester, you can just as easily use a digital multimeter set to the 20 volt DC range.

• Always take precautions to avoid electrostatic discharge by making sure you are properly grounded.

References

• Fred Morris: Replacing the VX800 Rectifier-Regulator