Alternator wiring issues
Maybe not a text book but it works at the very minimum. I just wanted to see if the alternator was doing its job.
What is the real test?
This is not a test and can cause damage, and here is why it is NOT a test:
"Let's say" the thing is partially charging, maybe has a couple of bad diodes, so your 45A alternator is now a "20A" alternator. You take off the battery cable and it still runs and you INcorrectly assume it is OK. When it is only putting out barely enough to run the engine
"Let's say" there is actually nothing at all wrong with the charging system, and you unhook the cable, it dies, and you INcorrectly assume it is bad. "Might be" it was just idling too slow.
DAMAGE. WHEN YOU UNHOOK a battery with a working charging system, this causes a voltage spike that is sometimes WAY over a safe level, and can damage electronics, especially in this age of EFI, solid state stereo, on and on.
MORE
FIRST determine what the wiring is doing and hooked to. I tend to dived problems into (no particular order)
The output/ charging line, that is, the wiring from the alternator output stud, thorugh the bulkhead, ammeter, back through the bulkhead, and to the battery
The field wiring, IE the wiring from the ignition switch to the volt. regulator, the VR ground, the wiring to the alternator field (70 and later) and so on
The components, the VR, the alternator, the battery
TO TEST: First determine if the alternator can output current, eliminating some of the wiring, and the VR. And, determine if the charge line is actually connected to the battery
DO DO THIS. "Rig" alligator clip/ other/ jumper wires. Disconnect the "push on" wires to the alternator field and "safe" them off, tape, etc. Rig a jumper to ground from one alternator field connection. Does not matter which. Rig a jumper from the remaining alternator field to the battery. When you connect/ disconnect the wire in subdued lighting, you should see a small spark.
Monitor the alternator output stud with a voltmeter. Run the engine slowly up in RPM. The voltage should rise from resting battery voltage (it may vary depending on state of battery charge) from something below 12 up through 12.6. When running, and RPM increased, voltage should rise. Do not allow it to go above say, 16V or so
IF THE output stud voltage goes WAY high, say, 20+V, move the meter to the battery and compare. If it does not "follow" and is fairly low---then you have a lot of resistance in the charging wire path, bad connection, etc
IF THE output does not rise, and remains the same as the resting battery, then the alternator is NOT charging. Find out why, or replace the alternator. First thing I'd do in that case is check the brushes. May simply be worn down