6 degrees outside, and my work truck decides that electricity is unnecessary. I opened the door, set my lunch box on the passenger seat, grabbed the ice scraper, and shut the door. Scraped the glass, but when I climbed back inside, I had no dome light. Weird. Key on, nothing there either. No crank, no headlights, no radio, nothing. Battery is sitting at 12.6-ish volts according to the multimeter, but I tried hooking up jumper cables anyway. Still nothing.
UPDATE: Fixed it. Voltage regulator. Previous owner turned some wiring into a rat nest, so I usually end up replacing the voltage regulator about once a year. I keep a spare in the truck. Usually it cranks but no fire, this time I lost EVERYTHING. Fucking weird.