When troubleshooting with the engine running it is important not to get your arm or clothing caught in the moving machinery. If the engine is stopped remove the keys or turn off the battery switch so that someone else doesn't start it.
If you have an internally regulator alternator I'm sorry to say I don't have many troubleshooting tips for you. You can test that the alternator is still connected to the battery by measuring battery voltage at its output terminals with a multimeter. Also check to see that the battery is not boiling hot or smoking. Other than that the next thing to do is to take it off and bring it to an alternator shop to bench test it.
Externally regulated alternators give lots more opportunity for troubleshooting. You can start in the same way by checking that you can still read battery voltage at the ouput terminals of the alternator and checking the battery is not boiling hot. Next you want to check that the regulator is working, it should have indicator lights or a display. If not check that it has power, normally on its black and red wires, and a signal to turn on, normally on its brown wire. The signal to turn on usually happens when the ignition is on, but sometimes it is hooked up via an oil pressure switch so in that case the engine has to be actually running.
You can test the regulator by measuring how many volts it is putting out on its blue wire. The plug has to be connected to the regulator to do that put you should be able to put the prongs of a multimeter in to the back of the plug. You are measuring with respect to the black ground wire. If its not putting out many volts this might indicate that the regulator is suspect but it doesn’t really tell you why.
If you have a Balmar regulator with a digital display then you can do more extensive troubleshooting. Consult the manual of your regulator for the exact details but the display normally scrolls through the following:
- Regulator name and model
- Battery type setting
- Belt load manager setting
- Stage in the program
- Battery voltage measured
- Calculated voltage desired
- Battery temperature
- Alternator temperature
You have to have the cheat sheet to read this data because the small display makes it a bit cryptic so get a copy of your owners manual or look it up online. Here are some suggestions on how to analyze the data:
Look to see that the regulator is reading the battery voltage correctly. Look to see that the Its desired voltage is higher than the battery voltage. Look to see where it is in the program. Look to see that the temperature sensors readings are within reason, the battery temperature should be more or less ambient temperature, the alternator is over temperatue above 105 deg C. If necessary disconnect the temperature sensors to see if that is the problem.
Finally you can test your alternator itself by "full fielding it" You have to do this with the engine running and so its important not to get your arm or clothing caught in the moving machinery. For this test to work you have to verify that the regulator is at least powered up because we are going to use its power supply to test the alternator. The easiest way to do this experiment is to unplug the harness from the regulator, and with a paper clip briefly jumper the red (power) and blue (field) wires. That sends 12 volts down the field wire which puts full load on the alternator and the engine should slow down very considerably with the extra load. Just do it for a second to test that the alternator is OK.
If you have one of the Balmar 6 series regulators and your external regulator has failed you can hook up the internal regulator which operates as a simple single stage "get you home" regulator. Instructions are in the manual, but in a nutshell they involve energizing the brown wire that comes out of the alternator.
Here is a video of the regulator display on a Balmar ARS-5 regulator: