ok. I checked the the wires for a current. there is a current when the car key is turned but the ignition is not on (on the yellow wire). so it should work yellow to yellow and red to red right? well for some reason id dosent. It olnly turns on when the red and yellow wires (all 4) are hooked up together. bonesninja i have a 95 honda civic
You're supposed to be getting key-switched power on the red wire and constant power on the yellow wire.
First of all, you don't need all four wires hooked together to make your system work. Get rid of that crap right now. You can get it to work exactly the same as it is now by connecting the red and yellow wires from the head unit to just the red wire from the vehicle harness. You won't solve your problem as long as you have the yellow wire from the vehicle harness tied in with the red wire.
Now, the most likely problem with the yellow wire is a blown fuse. Since you've also said that your vehicle clock isn't working, that makes the blown fuse scenario all but certain. Have you looked for the fuse labelled "clock"? Chances are, replace that and you'll fix the head unit problem too.
If you can't find the fuse, then connect the head unit's yellow wire to a different constant source. You can find a constant power wire at the key switch harness, or run a wire directly to the battery (making sure you put a fuse on the wire at the battery).
Whatever you do, DO NOT keep the red and yellow wires from the vehicle harness connected together. By doing this, you're mixing the two vehicle circuits. Everything in the car that's supposed to be powered from the constant circuit is now being powered by the switched circuit. If you ever do find and replace that blown fuse, then all your key-switched accessories will suddenly stay on all the time. Screwing up the wiring behind the head unit can affect the entire vehicle electrical system, not just the radio.