I had this exact problem only i was drivin at the time, Smoke was coming out under the dash aswell,
If its the same problem i had check on back of fuse box, And a big red power cable goes there which also goes up 2 the barrel,
If it is this you will see it all melted an stuff,
Mine was caused by the original wire that runs 2 stereo from light switch that dimmed the original stereo when lights were switched on,