I've installed two aftermarket stereos. Both acting the same. Once the car has set overnight, the stereo wouldn't power back on until I reset the battery, or unplugged/replugged the harness. I just purchased a new battery today, and hoping that might be it.

Just wondering if there is some kind of relay for the Switched or Constant power that may be causing this problem? It's just getting anoying.

 

The constant power should be just that.It holds the preset memory and clock settings.Are you using one of the radio adaptor harness's?With the radio harness diconnected and the key off check for power at the radio constant.I belive it's the orange lead and the yellow is for switched power.Look at the adaptor harness and see how it's labeled.

 

Using an adapter from an audio shop or walmart... your stereos wiring will have matching colors as the adapter so red-red which is switched power (IGN) and yellow - yellow (Constant/Memory) and so on and so on....