dodge charger radio

we installed in dash aftermarket head unit all works fine we just cant find a way to get a ignition + wire to come on with the key heard about a harness 7500 that will work or i thought about a relay from one of the computer turn on signals on redio plug , some input would be very helpful

You could always get the harness for the car.  But if that is not an option. Go to Southern Radio Supply (Southern Electronics)   Purchase an NTE 331 Less than $3.00.     Also get some Heat Shrink Tubing large enough to slide over the transistor.    Get 3 short pieces of wire  Blue Yellow  Red.   Solder the Blue wire to the Base    Yellow to collector     Red to emitter.        

There is a wire at the ignition switch that goes to 12 v when the key is turned on.  THis wire is not capable of powering anything other than this transistor.  Connect the Blue wire to this wire.  Connect Yellow to a constant 12volts.  The radio Memory wire is fine.  The Red is now your 12v switched.

Ths device will provide about 2 amps of capacity without a heat sink.   You must put the heat shrink over the entire transistor.  The metal tab has 12Volts on it.

Don't try tapping into the wire at the ignition switch without the transistor.  The car DOES NOT like that.

That vehicle uses a data-bus system.  When you turn the key on it sends a binary code to the radio that tells it to turn on.  Hence no switched wire. The harness does the same thing as a GM-24, it takes that data signal and gives you a switched output. I build the above mentioned  devices so we can add XM to these cars.