I had searched the forums and could not find any information on how the tape deck shuts off the radio when you insert a cassette. I did see questions as to how it worked, but none were answered. So if you want to be able to shut it off with the switch of a button, disconnect it, or whatever you can come up with, here you go. This was done on a CR-718, but there should be similarity with other like models.






When you insert a tape, it moves part of the housing that activates that green switch. To find the switch, you'll have to remove the tape deck from the radio and flip it over.

Next, lets say you want control the tape shutoff without inserting a tape. Maybe you don't have a tape, or maybe yours is difficult to eject a tape once its in.






Notice the slightly brown colored wire, closest to the arrow. We'll call that wire #1. Moving down from wire #1, wire #2 and #3 are the ones that, when connected, trigger the radio to shutoff and switch to cassette. Wire #3 appears to be the ground, but when I used a multimeter to check to continuity between wire #3 and a ground on the chassis, there was a small amount of resistance. I assume this is from various components in the radio, but not wanting to risk anything I just ran both wires out of the radio to a switch.






I hooked it up to a simple switch I got at radio shack, and now I have perfectly clear AUX in sound, thanks to this post:
http://www.brickboard.com/RWD/index.htm?id=1384202&show_all=1
This is my final install. No tape to get lost or stuck in the tape deck, just flip a switch and listen. I ran the wires underneath the tunnel that covers the shifter and the seat heater switches.