JCB 536-60 alternator light on but alternator is charging?

[Cobratom]

Has anyone had this issue with a JCB circa 2008. My Alternator charge light remains on and I get code D205 but when measured the battery is being charged and the alternator is operational. Could a bad ground cause it? Is there a voltage threshold?

The workshop manual is a bit useless on the subject.

 

[ACEngineering]

Has anyone had this issue with a JCB circa 2008. My Alternator charge light remains on and I get code D205 but when measured the battery is being charged and the alternator is operational. Could a bad ground cause it? Is there a voltage threshold?

The workshop manual is a bit useless on the subject.

Take the smaller wire off the alternator (not the W terminal the other one) the warning light should be out with ignition on not running, if it isn't then its shorted to earth somewhere back up the loom between engine and cab.

If it goes out with wire off not running then its working right so is likely an alternator fault.