Possible alternator and or voltage regulator issues?

1.....What is this 30A fuse? If you are talking about a fuse replacing the original fuse link, that is not nearly large enough

2.....Has the car been sitting awhile? Is the battery down? If so, the very first thing is to determine if there "actually is" a problem. Run the car and check battery voltage. It should not be above 15 at the absolute most. Normally, voltage, running, charging, should be (depending on battery charge and regulator / battery temperature) should be loosely 13--15 volts

Once the battery is warmed, and charged back up, things should be "tighter." In this case, you should expect not less than 13.5, and not more than 14.2

And to get even tighter, optimum is 13.8--14.2 volts

3...There is a couple of preliminary things you can do. Get a legitimate battery terminal brush if you don't have one, and remove and clean the battery terminals

Remove the regulator, scrape around the mounting bolts and the regulator flange, and remount, using star lock washers. The regulator MUST be grounded

Remove the alternator field wires and work them on/ off a couple times to scrub terminals clean and to "feel" for tightness. Do the same with the regulator connector.

Check your belt for tension and slippage!!!!