Hello! I have an 1994 (my95) RHD Subaru GC8 imported from Japan.  It has approx. 130,000 miles on the body,  and about 10,000 on a new EJ20 engine.  

All of a sudden while driving,  the aftermarket radio,  JVC kw-v850bt, stopped working and turned black,  the power door locks, and the cigarette lighter, and the dome lights also stopped at that time. The radio is connected to a 12" kicker subwoofer and AMP, 4 door speakers,  and two tweeters mounted on the front door frames. Those things were installed by Best Buy audio, and have worked for a year and a half. I have an under glow light kit with 4 led strips on it that was plugged into the cigarette lighter.  That was installed and functioning for a month before it had this issue. 

So far I've checked all of the fuses and relays inside and outside of the car and they are not blown, this was also checked by the Subaru dealer. Subaru said they didn't have a wiring diagram for it,  so they didn't want to touch it. Everything else seems to be functioning,  including the power windows and sun roof.

I'm by no means a electrical expert,  but I do have a multimeter. Any troubleshooting advice would be greatly appreciated!