Help solve my mystery? Couple weeks out of warranty

Check the actual wires that are feeding from the battery. Often corrosion occurs inside the casing near the battery. They connections can be tight and you would not be able to see the actual corroded wires. The simplest test is to tug on the wires to see if they move easier than they should, or cut back the first few inches of insulation on the wires to see if there is a bunch of corrosion.