11.89 volts with the engine running means the voltage is getting there from the automatic shutdown relay. That stands to reason because that's the same circuit that feeds the ignition coil and injectors. Since the engine runs, we know that circuit is working. The answer comes from the second terminal. Since the voltage is exactly the same, no voltage is being dropped across the field winding. That means no current is flowing through it and no electromagnet is being developed.
There are only two possibilities. The voltage regulator circuit inside the Engine Computer is defective or the wire going to it is open. It's more likely you'll find a broken wire. The next test is to measure the voltage at the Engine Computer. The wire is dark green and is in the middle of the three connectors. (I have to use a '96 service manual but I think the circuit is the same). There's three rows of pins. The dark green wire is the second from the end of one of the outer rows. There might be a protective cover that must be popped off so you can back-probe the wires, but don't totally disassemble the pins from the connector because they're real hard to put back together.
If you find voltage at the computer, the regulator is defective. You can verify that by grounding that wire with your back probe. That will cause the alternator to "full-field". Do that just long enough to verify battery voltage goes up. You'll hear the alternator strain too.
If there is no voltage at the computer, there is a break in the dark green wire. Start by looking for any connectors or places where the harness might be rubbing. There's also a splice in that wire. It's in the harness just to passenger side of the cruise control servo, and just to the right of where that harness makes a "Y".
Friday, February 11th, 2011 AT 1:54 AM