How to test the voltage regulator

You will need to test the charging system. Try this simple test, hook a voltmeter to the battery and check the voltage with the key turned off. Should be 12 volts. Now start the engine and note the volt meter reading at idle, it should go up to about 13.8 - 14.2 volts. Rev the engine up and note what happens. If the voltage is low at low RPM 12V and then goes up with more RPM like you stated it could be the regulator or the alternator. Start by switching out or trying another voltage regulator. If this does not fix the problem you will need to test and repair the alternator. The alternator out put can be tested by bypassing the regulator. This requires special equipment and know how. I hope this gets you

Hello there. My name is George. In regards to your problem, there are a few things you need to know. Make sure both battery cables and post are clean and tight. Also check the two bolts holding the voltage regulator onto the side of the engine. A loose voltage regulator will not have the proper grounding to function. Underneath the flywheel is a device called an stator. This stator creates an alternating current or commonly called A/C Voltage. This voltage travels to another external device called an Voltage Regulator. The voltage regulator converts the A/C voltage from the stator to Direct Current or commonly called D/C Voltage to the units battery. Using the Model, Type and Code numbers found on the valve cover, you can call any parts store and they should be able to tell you what type of charging system you have, (i,e. 10 amp, 20 amp etc.) Ask them what the A/C voltage should be coming from the stator. I believe it will be at least 28 to 30 volts a/c. You can measure this voltage by using an ohm meter set to a/c~volts. You must have the engine running full throttle when you do this test. The ideal rpms for this test is 3600.
You would need an tachometer to get it perfect, but full throttle usually gives an a/c output around 28 vac Now with the stator and voltage regulator disconnected and the engine running at full throttle, use the red and black test leads from the ohm meter and put the tips into the wire connector, red on one wire and black on the other. No, it does not make a difference which wire. Read the meter. If it shows the voltage the parts store told you (around 28vac is my guess, then your stator is doing its job. If it is giving you anything less than that the stator is bad. If it is bad, you will need to remove the flywheel to inspect it and or replace it. If its good, Turn off the engine and reconnect the stator and voltage regulator. Now find the single wire coming from the voltage regulator (its normally red) and disconnect it. This wire is the d/c voltage connection going to your battery. Set your ohm meter to d/c volts. Start the engine and let it run full throttle while you put the red test lead into the red wire coming from the voltage regulator and the black to a good ground. If you cant find a good ground then use the negative -(Black) battery post. If you read around 13 to 14 volts d/c then your voltage regulator is good and you have a shorted wire from the voltage regulator to the battery, If its bad then it will read 0 and it will need to be replaced. Feel free to contact me at: [email protected] if you have any other questions. Good Luck.

Use a voltmeter to test battery voltage with the engine running. If the alternator is working correctly, the voltage should read 13.5 to 14.5 volts DC. If reads 12.6 volts or less, the alternator is not charging the battery. Take the car to Autozone or similar business for a free checkout of the alternator. It might be a bad voltage regulator instead of the alternator.