First off, if the wires coming out of the unit have built-in fuse holder, leave those on, don't hack them off. I can't stress that enough. Some units have what appears to be a tiny fuse holder on the "trigger" wire, this in reality is a current limiting resistor encased in a plastic protector
Now, with that out of the way...
Yellow: constant B+, this needs to "see" +12 volts at ALL times. Connect this to the "BATT" terminal on the fuse box or make a good splice to the cigarette lighter power wire. Make this connection good as it provides the main current source for the output electronics.
Red: switched B+, the "trigger". Connect this to the factory original radio yellow wire. OR for simplicity connect it to the "RADIO" terminal on the fuse box. This should only have 12 volts on it in normal radio operating situations, i.e. the car is running, or the key is in the ACC position. The red wire "tells" the radio it's okay to draw current thru the yellow wire.
Black: A good ground. An old installer trick to see if you have a good ground is to crank up the radio with the antenna wire disconnected. If the radio doesn't go out, you have a good ground that isn't feeding thru the antenna shielding.
Blue with white stripe. This is a switched power line. It only puts out +12 when the radio is on. Typically used as a remote "turn-on" for a power antenna OR a turn-on for an amp or cd changer etc. More often an amp turn on is a solid blue, blue with white stripe usually indicates power antenna control.
[This message has been edited by Coppertop (edited 04-25-2002).]