alternator test?.... without ER visit

[Gordon Maney]

We need someone with a factory manual or schematic to identify the wires and terminals.

[KRB64]

I'll look it up if I can remember - a rainy weekend = chances are good my memory will function correctly, pretty weekend and I'll just go ahead and apologize ahead of time...

[QuantumJo]

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[QuantumJo]

This is from my 77 service manual.

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[Deathdeelr]

An easy test is to disconnect the voltage regulator and jump a wire from the small green wire on the alternator field coil to ground. This is called "full fielding." What this does is if there's full battery voltage at the red field coil wire, this sends full battery voltage through the field coil on the alternator causing the alternator to start charging at full voltage. When the engine is running in this state you should see anywhere from 14 to 18 volts at the battery. If this works and the alternator is charging in this state, so long as you have battery voltage on the small red wire, you can safely bet the regulator on the firewall is n/g or the regulator might not be grounded correctly. They ground through the mounting screws. I have a separate ground wire on mine due to the rust proofing on my firewall.

A couple of notes on full fielding tests. Remember to disconnect the voltage regulator before you do this. This test is assuming your wiring is good and if you FF the alternator with a good regulator in the circuit you're probably going to burn it out. Also, don't run this test for a long period of time. You could overcharge the battery and cause it to heat up and short or might create a blanket of hydrogen gas around the battery which could light up given the proper spark (either from connecting or disconnecting a battery terminal or if you have a lit cigarette in the vicinity).

[76WAGON200]

I just checked mine and it has blue and green field wires but the blue wire pushed on from the top and the green pushed on from the side. Before swapping alternators or regulators, check your connections thoroughly for loose, corroded or rusty connections or wiring. I recommend pulling the battery and working your way through the wiring from point to point with an ohmeter and checking your wiring resistance. Especially important is ensuring your grounds are clean and tight. The starter is a major junction point for the + batt and often needs cleaning and tightening. Good luck!