dood. whoever told you there is an internal fuse on your RCA is on crack.
The problem you are having is common with every pioneer head unit that has "dangler" rca's. The problem is Noise. If you look at the white plug with all the RCS's coming out of it, you can see which are positives and which are grounds,,, simple strip back any one of the grounds, and tap a wire onto it.
Connect the other end of the wire to Chassis ground, or to the ground wire.
I have never seen an RCA on a fuse. EVER in 15 years of professional audio sales and installation.
Good luck