I hate to spend money for a new radio. I put another salvage 712 in my 240, boo...it has its problems too. My harness coming up to the radio has 2 speaker wires, the big square connector and a SINGLE RED WIRE. The last 2 712's I had, had 2 speaker wires, the big square, and a DOUBLE wire connector coming down. This meant I couldn't plug in the double coming down, (orange,black) nor could I plug in the single red coming up. The first radio split between speakers, no display, but the tape worked. The 2nd played stereo much better, good display, but the tape was dead or not getting power (unplugged wires?)

I guess I need to realize these old 712's are shot and there is no sense trying to find a good one!

The orange and black wires have no function in a 240. Leave them disconnected. the red wire is a power antenna lead which has no function unless you have a power antenna. Make sure your speaker leads are grounded. The CR712 has uses the chasis ground for the speakers, so the white and grey leads on the car side of the plug should either be spliced into the black ground, or you should attach them to the screw on the back of the radio

You can tryt opening the radio up and taking out the tape section from one and put it in the other. It does come apart as an assembly.
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'75 Jeep CJ5 345Hp ChevyPwr and two motorcycles: it wasn't Volvos safety , it was Longevity that sold me