Battery is fine so I'm assuming its the generator? Any easy way to check this? And would you suggest converting to an alternator?
Easy way to check - stick your digi voltmeter across the battery terminals first after the car has been standing and then when the engine is running.
Before the engine starts the voltage should be 12.7. Could be a bit below that for an empty battery but if you are down at 10v or similar then susp[ect the battery. With the engine running the voltage should rise ultimately to somwehere round 14.5 volts. If the voltage doesnt rise - duff generator.