You need to test the car side of the harness for voltage. The yellow should always have 12V the red should have 12v only when the key is on. The yellow wire is what retains memory (IE saves radio stations, settings, time). The red is what turns the unit on. If you have them connected together, it is either not retaining your settings or the unit is always on unless you power it down manually. It depends on which wire you're connected to on the car side of the harness.