[growe58]

Most car radios have two lines going in hot. One is usually a red wire and provides power only when the car is turned on so you can turn off your car and not have the radio keep playing. The other is usually a yellow wire and is always hot and provides memory functions to the radio - station presets, clock, what spot the cd was at last etc. It sounds like the yellow wire is connected to a power source that shuts off when the car is shut off. You will have to find one that is always hot.

Buy a test light at an auto parts store for around $5. Connect the one side to a good ground and touch the probe to wires with the key off; when the test light illuminates, you have found the wire that is always hot.

Good luck!