I'm putting the stereo/wiring back to stock in my '85 S and I thought I had it figured out, until I realized that the DIN plug to go from the radio to the amps is 8 pin and the radio has dual 6-pin sockets! I have found mention in other threads of there being a Y-splitter that goes from the 8-pin to a black (rear) and front (white) 6-pin, which can actually plug in (in the rear there is a box which splits the 8 back to dual 6s for the amps). Naturally, I am missing this and I can't find any sort of reference to it or pinout (for the 8-pin) in the service manual in order to make a new one. Does anyone have any idea? Maybe one laying around?

 

These pin-outs and a schematic of wiring between components can be found here: http://foxed.ca/rx7manual/manuals/19...Electrical.pdf

Start on page 15-62

 

I have a hard copy of that service manual but nowhere does it have the conversion between the 6-pin at the radio and the 8-pin cable that runs to the joystick bypass and back to the amps, it seems to ignore that existing all together. There should be a straight-through for the single-amp base model and a Y-splitter for the trims with two amps but no joystick.

 

I think you can ohm out the short DIN cable that bypasses the joystick to find this conversion.

 

Okay, some progress was made. I rang out the wiring between the 6-pin plugs at the amps and the 8-pin in the dash with the joystick jumper in place. See below for the diagram - yes the 8-pin numbering is wrong (1-7 should be 7-1 but it was easier to jot down the notes while folded up in the car this way).



This supports the 6-pin at the amp being the same as the 6-pin at the radio - pin 1 would be R+, pin2 is +12, pin 3 is L+, pins 4 and 5 are R- and L- (this threw me off, didn't expect them bussed in-cable), and 6 is ground (it's tied to the shell as well, not shown in the picture). This means I can make the appropriate cable to go from the 6-pin sockets at the radio to the 8-pin in the factory harness. Someone please correct me if I'm wrong!

 

In conclusion - the 6-pin at the amps does appear to be the same pinout as the 6-pin at the radio, all the grounds and signal negatives are tied together, so it can pass all 4 channels and power through that 8-conductor cable via joystick. Since grounds are bussed in the cable and radio, it made for a pretty simple DIY cable, details below in case anyone else needs it (color was just for my reference, doesn't correspond to anything in the factory harness). As a disclaimer, I do not have the joystick (just the bypass jumper) so I don't know that this would be exactly the same if you did have it.

Diagram:

 

nice