03 Chevy Blazer RDS system upgrade?

Alright your best bet is to get a relocation harness http://autosoundgear.com/tek9.asp?pg=products&specific=jopoenq8 to move the radio to the trunk so you can retain all of its features. The harness will also give you all the connections you will need to hook up your aftermarket radio. Now the only thing you will need to do is find a switched + 12volt since the factory radio harness dose not have one. But since you want to hook up the Retained Accessory Power (RAP) you will use that as you’re switched + 12 volt. Now The RAP (Retained Accessory Power) relay is in the driver's side fuse box. Pull the relay halfway out, so it still operates, but you can carefully slide a test light or meter against the terminals. Test the terminals until you find the one that operates correctly. I think it is terminal #30, but not sure. After you have identified the right terminal, wrap a wire around it and reinsert the relay. Connect a small inline fuse 10 amps or so. Then connect the Switched + 12volt from the harness / radio to the other side of the fuse, and you're done. The reason for the fuse is so that if your head unit shorts out sometime in the future, the fuse will blow and of course your head unit will shut off, but at least the rest of the car's accessories will remain operational until you can repair the problem. If you have any questions or need more details don’t hesitate to ask.

I have never done that Blazer but I have done plenty of Class 2 Data bus systems which are almost all identical as far as wiring and components go. You can do the install without the harness but I do not suggest you do so.

Everything went fine,and sounds GREAT. stereo shop I had to get harness tryed to give me a relocation kit, Told them about this forum and all the info learned-they were puzzled with my dilemna. It seems that the 03 blazer(last year of  before trailblazer  came out) has a rds radio but it does not get as complicated as the newer rds radios.  I still had my door chime after taking the factory radio out. The Blazer harness does not have  switched 12v wire. so I ran a power fire from my fuse box(windshield wipers) to the new stereo. Thanks again to everyone who replied to this question. I really appreciate allthe help.

This system consists of                                                                                      Alpine 3DAW882  In dash 3 CD changer & Cassette (awesome receiver), 1 pair JBL 6.5 952S speakers(slim line for front doors) 1 Us Acoustics 4085 4-channel amp, 1JL  Audio 10 in subwoofer.

P.S This system really surprised me on the clarity and the power ( IT Rocks)

Thanks again everyone.