When you turn on the truck, look near your odometer for a number code. That number will tell you what faults are occurring. You can call the dealership and ask them what the number means or just message me and I'll tell you. I have the entire service manual in .pdf format. Maybe I can email it to you if you want it. If you need to replace the alternator, you need to drain all of the engine coolant too since it's water cooled. You can do this yourself but it's tricky and will take a good 2 - 3 hours. Bosch remanufactured alternators can be found online for $300 and up.