2001 buick lesabre stereo woes

2001 Buick Lesabre, no OnStar I'm installing a new pioneer head unit without harnesses, and I took out the old radio/cassette player. I've pinned down the 12 Volt Constant (Orange) and supposedly from what I've found online the yellow is 12 Volt Switched- But the stereo won't work if I hook it up as such. It only turns on at night! I don't know anything about the dimmers or lights, and I can't find a wiring diagram for the 2001 model. If I piggyback the switched with the 12 volt coming from my head to the 12 volt constant from the car, the stereo works, but stays on without the car being turned on. So, it isn't the stereo, I just can't find the true switched wire, assuming it isn't yellow. I also tried white, I found it labeled ignition from somewhere online, but that didn't work either. What the hells going on here? Am I missing something?

you hooked up the illumination/dimmer wire, hence the reason it only turns on at night (when your headlights are on). That car doesnt have an 12switched in the radio. you will have to run it from the fuse panel or tie into the accessory wire at the ignition switch. Another reason to buy the harness!!