rewiring radio

I just bought a 93 mazda and I can't find the factory wires for the radio so I decided to just run all new wire. The thing I need to know is Where should the red (hot) and the yellow (constant) be run to in the truck?

The Yellow should be ran to a constant power such as the battery or power distribution block. The red needs to be switched. you can piggy back off any existing switched power in the fuse panel that turns on and off with the key all it does is switch the radio on and off.

You can run the red to one of the cigarette lighter wires. I think it is only hot when the key is on and the yellow down to the fuse box to something that alway gets power or just run it straight to the battery +. Just my thoughts.

I was thinking it was along those lines, I just couldn't remember which way it had to go. Thanks for the memory jog.