i just bought an alpine cda 7894, and went to install it. I noticed that the wiring harness that comes with the head unit power wire is fatter than the one on the smart cable wiring harness i bought. This cable plugs into the back of the head unit and you don't use the factory one. then it plugs into a harness that mates with the factory gm one on the car....the alpine head unit harness power 12 volt wire is a little fatter, has a 20 amp fuse in it and some grey box? maybe a relay? i called metra the makers of the smart cables and they said they don't agree with the warning label on the power wire saying high current draw connect to fuse block or positive battery term. do not connect behind dashboard....what should i do

 

Connect behind the dash. They say that you should connect them directly to the battery becasue their internal amps is oh so powerful but I've installed about 3 or 4 alpine HUs like that and I've always connected them to the stock harness and never had a problem. Just remember if you do have problems down the road you know where to look first. If anything a fuse will blow and you'll have to run the wire top the battery but i doubt it.

 

I have that same HU. I've installed MANY Alpine units.. I've had them hooked up both ways; tThrough the Metra Harness, and direct to the battery. It really doesn't seem to make a difference, although some people have had noise issues with them connected to the Metra harness. I'd say use the Metra to start with, then if you get noise then try wiring it directly to the battery. I have mine wired to the battery, BUT I'm not running the internal amplifiers on that HU, plus it was VERY easy for me to the battery due to having the car tore apart when I put it in.