If the battery is full charged then the alternator is not going to produce much current anyway, its the way there designed to work. Try testing the current when you've got all the lights, fans, electrics turned on, the alternator should produce more current to deal with the increased demand.
The best thing i find for trouble some alternators is excahnge for a recon unit. you could try repairing it your self, but trying to get just one or two parts can be tricky and from experiance some alteranto designs can be right swines to get back together.