nonrev

The truck I'm working on is the 92 in my sig, it's started overcharging quite a bit (16.34 volts with my digital multimeter, battery doesn't seem to be boiling) I've tried running a ground from the alt case to the battery, no change. Do you think it's just the alt going bad or the regulator in the computer, and what would be a good way to check it?
I've read Cougars piece in the stickes about overcharging but I'm not really understanding how to do what he is talking about.
Cougar says,
I'm hoping this information will help anyone that is having a high voltage/overcharging situation or the flickering volt meter at idle issue. I'm using the external regulator diagram for simplicity, but the troubleshooting procedure isn't much different with the regulator in the ECM.
1st lets understand how the alternator works. The field winding creates a magnetic field. The strength of that field is determined by how much current (amps) is flowing through the field coil and not the voltage applied to it. As the field winding rotates, the magnetic lines of force pass through the stator windings creating an electrical current.
The regulator controls the output voltage of the stator winding by controlling the amperage through the field winding. The regulator is a variable resistor in series to ground. The regulator measures the input voltage to it and adjusts the field coil resistance to ground to maintain a stable voltage regardless of the amperage load placed on the alternator.
So what goes wrong. Anything that changes the voltage regulators ability so sense battery voltage will change the output of the alternator. The common problems are bad grounds and a voltage drop to the regulator.
Over time, connections corrode or wear introducing resistance into the circuit that lowers voltage to the sensing circuit of the regulator. This lower voltage is interpreted as a low alternator output, so the regulator compensates. Sense the regulator can't see what's going on at the battery, it doesn't know it's being overcharged.
To find out if your regulator is running blind to battery voltage, with the engine running place a volt meter on the field winding J2 terminal (that would be the one closest to the large ground lug) and to ground. It should be the same voltage as the battery. If it is lower than battery voltage, there is your problem. There are several connectors, an auto shut down relay if equipped, and the ignition switch that can introduce a voltage dropping resistance to the field. A quick check it to jumper the alternator output to the J2 field terminal bypassing the ignition wiring.
If the voltage check doesn't show a problem, start cleaning grounds. There are a lot of them.