I am installing a new radio. Now i took out my old one and it has 3 wires that would connect to the back. Now There is a yellow (positive/power for radio), Black (Negative or ground), and then grey( NO idea????)

Now my new radio is a Sony GT56UIW. On a side note i connected it and no display would come up on the radio but it would eject the cd.

And the directions are here http://www.docs.sony.com/release/CDXGT56UIW_install_EN_ES.pdf

So i am stuck on what is what and why it doesnt work. I really dont want to take it to a shop.

Any advice or diagrams on what to do. Or have anyone of you guys done something like this before?

Thank you

The grey wire is connected to the dash lights circuit and is controlled by the dimmer in the headlight switch.
I don't see an illumination circuit in your head unit diagram so you can ignore that wire in the car's harness.

The yellow wire from the head unit shoul be plugged into the fuse block at a "BATT" terminal.
There is no "always hot" wire in the factory radio harness as they didn't have electronic presets or memory on radios back in the day.

You should be able to get it to power up by connecting the red head unit wire to the yellow one in the radio harness and black to the black harness wire.

i tried switching the wires and nothing happened. Now the red wire is comming from the radio. The grey is from the car. Still stuck

Does the new radio have a 12v constant wire and a 12v aux wire?

They might both have to have 12v for the radio to power up.

Yeah you need to to put 12v constant power to the yellow wire on the new radio. 12v switched power to the red wire on the new radio, then obviously black to ground.

Like Twisted said you should be able to run 12v constant to the BATT terminal on the fuse block. You then will need to find a 12v switched source for the red wire, otherwise if you connected the yellow and red wires together you deck would always be able to be on even if the car is off.

^From the diagram.... Yes, it does have a "memory" powe wire.

Screw the old factory radio harness... We don't know if it's connected to anything at the other end.

The yellow wire from the new head unit harness should be plugged into the fuse block at a "BATT" terminal. (Extend the wire if you have to.)

Connect the red head unit wire to an "IGN" terminal inthe fuse block.
Now.... Connect the black wire for the new head unit to a dash bracket.

If it still doesn't work... You probably have a blown fuse in the radio power lead or at the fuse block.

ok and would the fuse have a red or white color on it? at either end??
and i just got a different one. and no instructional videos?

You just got a different what?

ok and would the fuse have a red or white color on it? at either end??
and i just got a different one. and no instructional videos?

the fuse should be right below where the harness plugs into the back of the deck, should be a blade fuse. Probably red with a white #10 on it.

yellow-12volt constant..memory wire
red-switched 12volt acc.
black-ground