1992 Mazda b2200

Electrical problem
1992 Mazda b2200 4 cyl Two Wheel Drive Manual

I recently changed the factory radio to an aftermarket radio. After the installation was done I noticed that the dash lights and the tail lights were not working. The fuse was blown and when I replaced it it blowed again. I got a volt meter and checked continuity. There is 12v on the primary, but when I turn the swith on the secondary goes to ground. I removed all the lights and still no change. I unhooked the new radio and still no change. Any ideas?
June 7, 2008.

What fuse is blowing is it the room fuse 15amp or the cigar fuse 15amp? I viewed the illumination circuit you could have shorted out the blue and red wire going to the radio-

Jun 7, 2008.
The fuse that is blowing is the 10 amp that is located in the tail slot. Top right slot of the fuse box.

Jun 9, 2008.