Alternator wiring diagram?

Be sure the voltage regulator is bolted solidly to the body too. It needs a good ground to work.

Sorry to leave you hanging. Have you solved the problem yet? The green / red wire provides the turn-on signal for the voltage regulator. With the plug disconnected you'll be reading the 12 volts that comes through the ignition switch and dash warning light, (or a resistor that replaces that light on some cars). It went to near 0 volts when plugged in because the regulator was grounding that wire to turn on the warning light. When the system is working about 6 volts appears on the white / black wire to tell the regulator to turn the warning light off. THAT'S when you should again find full battery voltage on the green / red wire.

Look for a yellow wire in the connector. It should have full battery voltage all the time. If it doesn't, a fuse or fuse link wire is blown.

That connector is part of the voltage regulator. It's held on with four small bolts in a rectangular pattern. If you can see back there, you'll find two additional bolts. One might be covered with a plastic cap. The other one has printing stamped next to it that says "Ground here to test". Use a piece of wire to ground that bolt while the engine is running. If the headlights get brighter and the system voltage goes up, the regulator is defective and can be replaced separately. If there's no change in system voltage, further tests will determine the cause but worn brushes are the most common thing to find. They come as part of a new voltage regulator. I can walk you through the testing procedure. You'll need an ohm meter or test light.

The charging system is not working and you need to determine why.

There's two different generators for your car. I got sidetracked searching for a diagram with the correct wire colors on the external regulator version. For now, jumping between the "I" and "F" terminals on the regulator will bypass it and "full-field" the generator. Those should be the first and fourth terminals. That will make it charge wide open if the regulator is at fault. Don't raise engine speed and definitely don't disconnect the battery when doing the full-field test. Either of those things will allow system voltage to rise to dangerous levels if the generator is working.

If bypassing the regulator makes the generator work, you'll see the head lights get noticeably brighter, or, if you're monitoring battery voltage with a digital voltmeter, you'll see the voltage go up to around 14 to 16 volts at idle. That will prove everything other than the regulator is working.

If bypassing the regulator causes no change in output voltage, the problem is in the generator or wiring. I can walk you through that diagnosis once I find a diagram.

AGGHHH! Do not disconnect the battery with the engine running! That was a poor man's trick done many years ago by mechanics who didn't understand how charging systems worked or how to diagnose them. The battery is a key component in regulating system voltage. You are lucky your generator isn't working. If it was, and you raised engine speed, it is possible for the output to go to over 30 volts. Computers can not tolerate that kind of voltage and the voltage spikes that are normally dampened by the battery. While a 1989 model might not suffer irreparable harm, newer cars can have up to 47 computer modules. If enough of them are damaged, the car may be not worth repair.

The place to start is by measuring battery voltage with the engine running. You must find between 13.75 and 14.75 volts. Based on the symptoms, expect to see less than 12.6 volts verifying the dead charging system. How was your generator tested? Also, can you describe the connectors on it? Do you have a plug on the side with two fat black wires with orange stripes, or do you have a single fat black wire bolted to a terminal on the back?

Caradiodoc

You really need to check output of alternator first which autoparts do for free. But also check if the fusiblelinks are any good that may be the reason as well.

Are you sure that your purchasing the correct amperage alternator. If you try to buy one that isn't capable of supplying the needs of the vehicle your esult will occur. Try buying a new alternator not reman. It's usually the voltage regulator that goes anyway.

Charge System light still flashes. Load test the alternator and double check connection at alternator and battery.

A good battery should be 12.8 volts when load tested should hold 9.6 volts in 10secs if not it needs replacement.