How do you test the power of an aftermarket radio without hooking it all up?

To test the power of an aftermarket radio without fully connecting it, you can use a multimeter to measure the voltage at the power harness. Connect the red probe to the power wire (typically the red or yellow wire) and the black probe to the ground wire (usually black). Ensure the radio is turned on, and it should read between 12 to 14 volts if it's receiving power correctly. Additionally, you can briefly connect a battery to the power and ground wires to see if the radio powers on without completing the full installation.