I got my '91 alt last week. put it on that moment. I knowticed that the 2 wire clip that pluged into the back of my old alternator, is now on the top of the new alt and it is a totally different type of connector. anyone know what wires go where on this socket I am going to get the plug from a yard.
thanks

 

Same wires, just need to change the plugs. Go grab them off the harness at the junkyard.

MikeL has a series 6 alt (100+ amp) on his S4, and the install was just like the S5 alt install, so i think im going to go with that setup over the S5 swap.

 

The wire that went to the top terminal on the back of the early alternator will go to the left terminal on the top of the late alternator, when looking at it while standing in front of the car.

Yea, with the S6 being only $10 more than the S5 at my local auto parts store, I went with the S6. You might be asked to pay a core charge though because you'd be turning in a different alternator.

The only problem was the pulley and spacer. I managed to make it work with nothing but a drill press and a chop saw.

S5 on S4: http://brfoundation.com/RX-7/alternator.htm

S6 on S4 or S5: http://brfoundation.com/RX-7/alternator2.htm

Brad's S6 on S5: http://www.geocities.com/rx7_ragtop/alternator.html He used a single groove pulley and didn't have as much trouble as me.