Charge light on and not charging.

Battery supply is available on main battery stud.
Terminal S on regulator has battery supply voltage.
Terminal L appears to work the charge light. Terminal FR has a constant 4.5 volts at all times.

The dealer conducted continuity tests on the wires between ECU and alternator, all tested OK.
Initially the local dealer swapped the alternator for another, no change. After a long wait a new ECU was obtained and fitted. I was told at this point that the charge light went out and the vehicle was charging.

Soon after the customer returned the vehicle with the same problem.