I know that most of you buy Metra Harnessesn and stuff like that to connect your new stereo.
But I'm in the middle of istalling an Alpine system in my Sc400 and I'm working with a guy who does Cobalts and every kind of car.
What he told me is this.
He wants to take the power wire that goes to the stock amp OUT OF THE TRUNK and into the dash to power up the headunit.
And then run a new wire that he's gonna buy at radioshack he says it comes with a high capacity fuse and run that one from the battery strait to the trunk to power up teh 2 new Alpine amps.
He did that on his Cobalt but I told him Lexus is Different you need to use the Metra harness but as this looks I think he's right.
But I don't wanna do it because if it's so easy then why is everyone here buying Metra harnesses.
I plan do do that and run rca wires from the headunit to the amps for signal.
That will be MUCH simpler but I still wanna ask why u use Metra harness maybe it's because the car has positive ground or something I don't wanna risk so that's why I'm asking.
And also I have to split one channel from the main amp to go to the sub but I wanna buy 2 rca splitters to split each channel but connect 1 to the sub amp and one will stay unconnected.
Because I have a theory that if I only split 1 channel so let's say I split the left channel and not the right the right channel will have MORE POWER then the left so that's why I wanna split both channel but connect only one.
But the guy who helps me said that it's dangerous to leave a connector unconnected because if something metal comes in contact with it my trunk will catch fire.
Is this TRue????
Please help me because these are alot of things that I haven't anticipated so I wanna know if I'm doing the right thing or not!!!

 

The harness is used so you dont have to cut your factory wires to install the deck. If you pull the power wire from the trunk to power the deck you will also need to find a switched power supply (on only when the key is active) and a ground point. If you run a new ground for the deck, depending on where you ground to, you may create a ground loop which will cause noise to enter the system. I would just spend the 20 bucks use the harness and save your factory harness in case you ever want to go back to stock it will be a plug and play thing.

just my $0.02

 

Find a new installer. Any trained and MECP certified installer will either use a proper harness or be able to tie into the existing harness by testing the lines.