Charging system troubleshooting
Engine running at high idle (2000 rpm) the alternator puts out 12.07V; Batt is 12.2V.
Only comment here is to think of it the other way. Battery is 12.2 Volts. Alternator stud is 12.07 V. Therefore current is flowing from battery.
Probably 2 to 5 amps flowing out of the battery (as seen on the ammeter).
Engine running with headlights on the alternator drops to 11.53V; Bat is 12.0V.
That's not a terrible ammount of resistance. Around 10 to 15 amps flowing and less than a 1/2 Volt drop in the lines.
With Key On, Eng Off the one FLD wire registered 11.37V. This could be one issue; expecting it to be closer to 12V
Ideally yes it should be same as battery. Showing more resistance in the circuit from the main splice to the field wire than you saw with the power to the headlights. Key switch connector, bulkehad connectos, other? However it doesn't explain the lack of charging.
If I interpret correctly the the blue field wire is the one you tested - the one spliced into the 'ignition' circuit.
Reconnected it to the alternator, removed the other FLD wire and grounded the spade connector to the alternator. With engine running, charging voltage still 12.07V at alt Batt; ammeter still discharging.
Grounding the spade terminal should have full fielded the alternator - and yes it should have started producing power.
Second test, kept the first FLD grounded, disconnected the 11.37V FLD and jumpered over to the Batt +. No change in alternator output.
So it should be the alternator, correct? Removed it and had it bench tested at O'Reillys. I stood next to the guy and watched the test, the alternator passed! Tried it twice.
Interesting. (not in particularly good, but still interesting) What sort of test did it pass?
Got a couple suggestions.
I assume the alternator is still off. Measure the resistance between the field terminals. This just makes sure its not an open circuit.
I'm going to assume you don't have a low current ammeter. So if you want to more on the bench, only things can do is check the brushes and then open it up, remove the stator and check it and the rectifiers. Pretty easy on the square backs. I posted a thread with some photos if you want to get a sense of that - just ignore the pulley removal stuff.
Rig up test lamp you can splice in-line with the field circuit - one side could have a female terminal to slip on the alternator spade - the other an aligator clip.
Run the engine with the test lamp in line. If the lamp lights up then current is going through the rotor and it should be making a magnetic field. based on what you've done and what you have available to check - that's the only thing I can think of.
