Battery charging

Be a little more specific.
Does "Checked" mean "Looked At", "Disconnected and Closely Inspected"  or "Measured Voltage On" ???

You need to make some measurements of resistance and voltage.I have seen problems with the terminals that plug into the regulator. This is what I would do:

1. With the engine running I would measure the voltage across that battery, it should be approximately 14Vdc.

2. Measure the voltage across the regulator capacitor. It should also be about 14Vdc.

3. Measure the voltage across the 2 generator terminals on the regulator. It should be about 20Vac.

4. Measure the resistance between the 2 generator wires. The values are in section 3.12 of the heavy maintenance manual. The generator coils will be very low resistance < 1 ohm. I would wiggle the wires to make sure that there isn't an intermittent problem.

That should be enough to get you started. I've attached a standard regultor connection diagram. Your installation my not have a warning lamp and you may have an ammeter shunt on the output.