External/ internal crossover, Inline fuse

I have a JVC AR-5000 radio and a kenwood KD748 amp, I used the sub output to run to the amp and from there to the sub. My friend told me that you cant use the internal crossover on the radio with the crossover on the Kenwood 748 Amp. My friend said that if I quit using the sub output for the subs and used the regular rear speaker output instead I would not be at risk. (I'm currently not using the rear speaker output) Do I even have a crossover in my JVC AR-5000 radio? BTW I have been running my radio and it sounds fine, I just dont want to mess anything up by running 2 crossovers. And my other question is what size inline fuse should I use for my acc and my constant power that runs to my radio? The radio that I took out of my truck had a 1 amp fuse for the battery and a 3 amp fuse for the acc... Is this right? Thanks for the help

Well, as far as the crossovers,. you will not need to worry about running two of them inline.  It does not affect anything on the deck or the amp, it will however limit some of the bass because it would have to pass through two of them.  Your deck does not have an internal corssover though.  I would not change anything on your set-up and I am not quite sure where your friend got that information from.  As far as fuses, I would put whatever the deck requires.  If it is not blowing the fuses don't mess them.

actually, I take that back, after reading a little more on the specs, it does have the crossover.  I would just scroll through the menus and turn it off.  That would be the best thing.  Use your amp for the crossover, it will usually handle it a little better.

Hey Thanks for the reply, I have looked and cant seem, to figure out how to turn the crossover off on the head unit... the directions dont even mention a crossover, I have turned the internal amp in the head unit off. My friend said that I need to put my head unit on flat and adjust the settings on the amp.... I think that would really stink to have to go to the trunk to adjust my settings. I have the input sensitivity on medium, and the frequency (HZ) goes from 50 to 200 I have that set on 80. (on low pass) If I turn that to 50 which is as far down as it goes, it practically shuts off my subwoofer, even if I have the head unit bass all the way up

You lowpass is your subwoofer crossover.  As far as having to go to the trunk to change it all the time, once you set your crossover, you shouldn't ever have to touch it.  The cross over eliminates the highs out of the sound and just allows the low bass to pass through.  A general setting is just to have it right around 80hz.  As far as setting the deck to flat and just adjusting the settings on the amp, that eliminates the whole reason to have the EQ in the deck.  There is a few posts on setting the gain on the forum, follow those directions and go from there.  It is worth it and you will end up with a nice clear low bass.  You might want to turn the internal amp in your deck back on also.  That shouldn't affect the sub.