why did my radio, 12 volt outlets, and rear defogger all stop working

Question, what is voltage on both sides of the fuses with ignition on and off and when starting engine. If all checks good 12V. To 13.5 then I would do same voltage test only this time put your vom in between the ground cable and battery negative. Simply take the negative battery cable off and set vom to read at least 20 volts connect the vom leads between ground cable and the battery negative post. Mare sure there is nothing powered on in or outside of car. Like doors shut so no interior lights, just make sure everything is off..if so you're vom will be reading nothing, no voltage flowing from the battery. If there is voltage showing then start pulling the fuses only one fuse at a time, if pull a fuse and no change in voltage showing then place fuse back and move to the next fuse and do the same with all fuses until the fuses pulled and the volt meter dropped back to zero no voltage flow. This is the circuit that has the problem, now trace the circuit wires and no problem with the wires then what ever there connection with has a problem. If you find no power flow at all then good you don't need to check out the circuits for shorted wiring or device. Now if you have power to all fuses 12V or over with no drop on both sides of the fuses and you find no grounds or short in systems then you have a open circuit. If that's where you are at then you need a good schematic for the devices you have a problem with and find the common denomater, there has to be a common that connects these devices either common ground or common power supply. I would look for a common ground to start, most logical is bad ground. The entire process should take less then 2 hours, actually you can have it trouble shot and repaired or part ordered in 2 hours. Good luck. Randy CO