Radio Fuse Keeps Blowing

[NWA_Dave]

2007 SR5:
I have a newly installed head unit, was working fine for a couple of weeks, installed it with a harness adapter from Crutchfield.

The other day, the Radio 1 fuse (under the hood) blew. I just checked it today, and when I install a new fuse, it blows immediately. It does this when the key is NOT in, so I'm confused...shouldn't there be no power in the circuit when the key is off?

 

[riceandpho]

take the radio out and check the harness itself, you might have a chaffed wire. how is it even hooked up, hopefully its crimped and not using wire nuts.