[patrickt]

And the charging light is not lit... ok put a voltmeter on the battery with the engine running at 2000 RPM and confirm your getting 14+ volts. If you are, and your ammeter is still showing a discharge then we'll need to put an inductive ammeter around both lines, and the fat brown wire that leads to the bottom of the circuit breaker from the solenoid, to measure the current in each. The current in the fat brown wire will equal the sum of the original ammeter wire and your new shunt wire (that's Kirchhoff’s Law). The difference in the two will be in proportion to the resistance of the two. What you are looking for is to make sure there's no unusual amount of resistance in your ammeter wire.