Run a 10 gauge wire directly from the large post on the back of the alternator to the large post on the solenoid where the positive battery cable is connected. You can leave the dash wiring alone. By using a thick wire like this, the majority of the current doesn’t go through the smaller wire at the firewall junction, reducing the chance of problems. You will notice the ammeter no longer does much after this but that’s no big deal.
Take a voltage reading at the battery with the car running before you add this wire and afterwards. You will see a nice improvement because the smaller factory wiring has a lot of resistance which drops voltage. Ideally, you should see voltage at the battery around 14 volts.
