>>It isn't doing the job as the voltage at the battery is not indicating a charge when it is running.<<
Could you be even a little bit specific. An actual voltage reading.
My Ammeter reads "0" all the time. If it reads anything else, I know I have a problem. By anything else, I mean neg or positive.
It usually drains very little current from the battery to start the truck. That small drain is replaced very rapidly. Driving down the road, the ignition and radio draw very little current from the battery. The generator or in my case an alternator has to supply very little current to maintain the battery. That means the ammeter shows a very small or no reading. It will however, maintain 13.5 - 14.5 Volts across the battery when the engine is running and 12.5 V with the engine off. With your generator you should check the voltage at a high idle..
When an ammeter begins to show a charge above the normal reading, it is usually time to find the battery warranty and see how old the battery is. It means I have one to three weeks before the battery dies. That is why I prefer a dash ammeter as opposed to a volt meter. A volt meter on the dash will continue to show 14 V up until the time the battery has died. No warning.
The iron poles in the generator retain a residual magnetism. If the polarity of this magnetism, north - south is switched the generator will try to charge in the wrong direction. This will destroy the regulator and generator. A generator is "polarized" to correct the polarity of the magnetism in the poles. Once a generator is installed, wired properly and polarized, it does not need to be polarized again. That is unless you do something to reverse the polarity.