Trailblazer 2003 12volt

Hello, Just got my new trailblazer and i heard that you cant use the 12 volt acc on the gm wiring harness and that you have to get it else where. Can anyone help me out here, where is the best spot to get the 12volt acc from and is there anything else that i should know about that is different in the 2003 trailblazer. Thanks guys

I think this vehicle uses the Class II wiring system, which means if you remove your factory head unit you'll lose some computerized functions of the vehicle.  Most notably, the door chimes reminder that sounds when you accidently leave your lights on or the keys in the ignition, will not be heard if you use a regular harness.

There are a couple of different integration harnesses out there but I recommend the Best Kits BHA2004T because it completely integrates with the stock system and lets you keep all of the computer functions.

Also I should point out that depending on whether or not your vehicle came with the bose system and/or the On-star system, you may need one of these special adapters instead.

Sorry I kind of got away from your main question....yes that is correct, there is no +12 volt switched ("accessory") wire in the radio's harness and so if you hardwire stuff (which I highly recommend against) you'll need to get your switched power from the ignition harness.  It should be an orange wire, but make sure you verify this with a DMM first before connecting to it.

Thanks Ethan for the great info it helped me out alot!

my switched power wire should only show 12 volt when the key is on acc or car is on? is that correct?

Thanks,

Yep that's exactly correct.