[TurboBRZ]

The other night I was soldering in a 4-channel amplifier RCA adapter to the radio harness in my BRZ. I had completed all 8 wires for the 4 speakers plus the remote turn on for the amplifier, and then I said "why not connect that optional ground on the adapter to make sure there is no distortion?".

So I got out my power probe and hooked it up to the battery, and then I went to my radio harness to see which of my wires was a constant ground. I tested the wire with the accessory power off, then turned the accessory power on and tested it again - it was a constant ground. So I turned off my accessory power and wired the optional ground to the radio harness (keep in mind all systems were working perfectly until this point).

I then plugged in my radio and put it in my dash, hit the ON button and nothing... No power to my dash, no power to the radio - and no accessory power. So I began checking fuses. The Radio (interior) and MPX-B fuse in the engine bay were blown. So I cut the new ground wire I had just soldered in (undoing my last step) and put a new 7.5A fuse into the MPX-B slot. The moment I put in the fuse it popped.

I got my multimeter and tested the voltage through the MPX-B fuse, which is fluctuating between 8-9V with the fuse blown. The amperage is very low (below 100mA). I then tested the other fuses in my engine bay and interior - none of them are drawing any voltage - the meter reads 0.00. I am now trying to figure out how the fuse could blow with less than 100mA present...

I'm now waiting for some new fuses to arrive as no one sells packs of the 7.5A fuses for this car! Gotta love Toyota and Subaru for that one - considering there are literally 20 of these fuses in our car. Just wanted to post this and see if anyone has any insight. I can't comprehend how wiring a ground to ground caused the fuses to pop, nor how the fuse popped again after I cut the wire I had put in... Everything done up to that one wire worked perfect. Now nothing works.