I'm Trying to hook up my amp to my factory head unit for my subwoofers. But I have security system that allow head unit to shut off when batter is removed from it. How do i solve that problem. And also if I get a new head unit, do I need factory head unit. I heard you need those cause air bag goes through head unit or something like that.
I don't know what car you have so I'll suggest you call a local audio shop and speak to an installer. tell him the make/model/year of your car, and ask him for details on replacing the factory head unit with a new aftermarket model.. what will you need? is it as easy as new harnesses and a fit-kit? does the airbag system, keyless entry, or alarm use the head unit in any special way and if so, how is it bypassed?
otherwise, keep the factory stereo, high-level/speaker level inputs to the amplifier from your rear speakers, and you should be able to wire the system without pulling the battery cable if you're careful, and the last thing you do is put the in-line fuse into the +12V line at the battery. then you can add a ring terminal to the battery post and not have to pull the terminal at all. This should hopefully bypass the battery disconnect protection circuit. (I hate that crap, personally.. who the hell wants to steal a factory stereo in the first place? that'd be like a blessing if you ask me! heheh) good luck.
ok if you're wiring an amplifier, you'll be using an amp wiring kit. that will supply you with some (usually 4AWG) heavy power cable that is used for grounding the amp, and for running to the positive battery terminal. the last thing you do is actually connect the power to the battery. so, mount the amp, run the signal lines (RCAs) and remote trigger which will turn on your amp. then ground the amp to bare chassis metal within two feet of the amplifier, keeping the ground cable as short as possible, and using the same gauge cable as you use for the main power line. now, route your +12 line from the amp to the car's battery positive terminal. you'll want a fuse holder placed about 18" from the battery, and leave the fuse out of that holder for now. loosen the bolt on the positive battery terminal, or get a second nut for the post-bolt. do not remove the battery cable from the battery post. the amplifier's +12 cable should have a ring connector on the end of it. slip that ring connector over the battery terminal post-bolt, and replace teh nut, then tighten it down so that the amp's +12 line is now connected to the battery terminal with the main power cable for the car. tighten down that bolt again, and now, you're ready to install the fuse in the fuse holder and give power to the amplifier. all done. it's really pretty simple, all in all. the hardest part is finding a rubber grommet in the firewall where you can snake that 4AWG line through from the engine compartment to the passenger cabin, then finding plastic trim and carpet to hide it under so it looks professional.
wire the remote trigger line from the amplifier to an ignition line that has +12VDC when the keys are in the ignition. that will work. use speaker-level inputs on the amp from the rear speaker leads for signal instead of RCAs.
yeah speaker level inputs just about always sound like crap to be honest, but you have no choice since you're keeping the factory radio. The only way to get true RCA level pre-outs from the source is to get a new head unit, and probably new front and rear speakers as well, since many factory systems use proprietary speaker setups like 10 Ohm speakers, or self-amplified components that won't work with aftermarket radios.
factory radios don't have RCA pre-outs anyway. you're restricted to high-level inputs for teh amp if you want to add an amplifier to a factory stereo. That's why most people replace the head unit too.
Right now, i'm planning to buy sub and amp. Then i will upgrade my head unit later. And I was looking for line level converter and I saw many kind of it. Which one should I get??