Chrysler Repair: Blowing 5amp Fuse, kenwwod, radio wiring

Question
1994 Labaron GTC Convertable 3lt. Auto Trans.
Vehicle has an after market Kenwwod AM/FM/CD.
Problem: If you turn on the headlights, the intstrament panel lights and the radio all at once, the 5 amp instrament pannel light blows.
The radio if the volume is turned up over 20 shuts on and off. At times wipping out all preset stations. Look forward to your reply.
Thanks Ian  

Answer
It sounds like the circuit for instrument cluster illumination is shorting out, possibly internal to the radio or the after-market radio wiring that taps in to factory illumination.  If you unplug the radio and turn on the headlights does the fuse still blow?

The over 20 setting could be excessive current draw through the radio, I would want to know where they tapped in for the powering up of the radio.
Doug