Been having OVER charging issues with my new alternator and was told the ECU controls voltage, could be wrong? I thought the voltage was regulated via the alternator?

Anyway, the voltage in my 2003 Protege DX 2.0 Automatic has been spiking up to 18volts at higher rpm and causing issues.


I need an ecu (I think)for my protege and noticed that there are 4 different variations, with the only difference is 1 letter at the end. For example.

FSAF-18-881 FSAF-18-881A FSAF-18-881B FSAF-18-881C

Looking on eBay they seem to be all the same for my year but want to know how they are different?