If she has a power ant., find the wire that controls that, and splice it down the wire and hook into that. It's usually blue, but make sure you double check in the owner's manuel, fsm, or chilton's if your sis has one. The yellow wire that you hooked into is probably the constant wire (for the clock), and was probably run in a series with the cd player controller. Find the antena wire, and splice into that.
Disclaimer: I'm in no way responsible if you break your sister's radio, but will take her out for dinner if need be.... .
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"Pure adrenaline attached to a license plate. Isn't it time to experience one yourself?"
-Dan Gurney
Turbo for Sale