I have replaced the alternator on my truck in brand new battery but The alternator is still not charging .

Hello, Dave here, contributing to RepairPal and providing expert advice since 2010. I do not know of any part under the fuse box that influences this system's charging. Your alternator produces adequate amperage and has the voltage output regulated via the powertrain control module (PCM). Desired and actual output voltage is measured and then regulated as needed. What testing has been performed to check alternator output in voltage or amperage? Has the replacement battery been tested to ensure it is fully charged and able to accept a load? If your charging system is putting out proper voltage and amperage and your battery is good and accepting load and charge - all would be well. Please share testing and what is missing? https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.