Hello everyone, I am looking for a solution. I sent my car to the shop for a battery relocation in 2023, and it has only been driven about 3,000 km in almost two years. The shop installed an RX-8 alternator in my Series 4 (S4), and everything was fine until I decided to redo all the battery wiring, rerouting it from under the car to run under the carpet.

One day, the alternator output dropped to 12V while the engine was running. I sent the alternator for a rebuild and installed the newly rebuilt RX-8 alternator. Initially, it showed a consistent 14.5V with the headlights, gauges, and CarPlay on—except when the electric fan was running. However, the voltage dropped back to 12V again overnight. I took the alternator back to the shop, and they told me that the voltage regulator had burned out.

I also asked for advice on Facebook, and most people told me that the RX-8 alternator is controlled by the PCM, unlike the RX-7 FD alternator. They suggested that switching to an FD alternator would resolve my issues.




I have a question:
Can I use only the stock FC alternator output wire, which connects to Terminal B on the FD alternator? I have a leftover 0-gauge wire. Can I use only the 0-gauge wire from Terminal B on the FD alternator, or can I connect both wires together?

For Terminal S on the FD alternator, I plan to connect it to the distribution port (which is connected to the battery positive) with an inline fuse. For Terminal L, I plan to connect it to the stock FC ground wire only.

Would this setup work properly?
I also noticed my pigtail have residue onit.

 

If you have a stock harness connector on your car, there are many threads on here on how to FD swap an FC alternator. The adapter pigtail for the conversion is for sale online as is the proper pulley if needed.you don't have one already.