I just bought a 2001 S40 1.9T and I'm going to install my amp/subs in the trunk. I've installed 4 systems before in previous cars and friends' cars, and the one thing that's always caused me pain and suffering is finding the best hole in the firewall for the power cable. I'm going to be using 4 gauge cable, and for the time being, just running speaker-level inputs to the amp from the rear speakers. If this turns out to sound bad, I'll run an RCA from the head unit later.

So my question is, what is the best way, in your opinion, to run the power wire from the battery to the trunk, specifically through the firewall, but any more instruction would be appreciated, as I have never wired an S40 before and it would save me the trouble of having to wing it and figure everything out on the fly. Thanks

 

I haven't done an S40 yet but look for a rubber grommet you can use.If all else fails drill a hole and install a new grommet.

 

thanks, i found a rubber grommet about 3 inches diameter in front of the glove box that has a 1 inch thick bundle of 18-20 gauge wires running through it, meaning plenty of room to spare for a thick 4-ga cable. it ran right to the passenger floorboard no problem.

 

Cool I bet it will sound good!!!

 

Now the only problem i'm running into is with the RCAs, or lack therof. I'm not going to run an RCA until I get a new cd player (right now, i have factory). I figure that I have to use a high-to-low level converter to adapt the factory head unit into RCA plugs, and there are speakers with wires hanging down from them on the rear deck of the trunk that are those exact cables that I'd be using behind the dash. I decided to tap into these and use the high-level inputs on my amp, but lovely MTX can't just put screw-down connectors for that on the amp as they do for the outputs and power leads, they have to use a special connector I need to order from the factory. Just great - something to buy that I won't need when I get a new cd player.

 

Just go to radio shack or walmart and buy the speaker to RCA adapter and use that.
It is cheap and they will have it in stock.