BCC and lack of coach charge with engine running

[kennyrodgers]

Hi Folks, just putting this one out there.
I've noticed that the alternator is not charging the coach batteries whilst the engine is running on our 94 Southwind. The handbook says it ought to.

The aux start / charge relay works and energises fine when you press the switch on the dash (voltage is present at the two small wires) however with the engine running only there is no voltage present at the two small wires so the battery sets are not coupling. I've traced the + wire back to the plug on the board and there's no voltage in the connector either. The aux start fuse is fine.
I have a BCC trouble shooting guide and it says that "any deviation from charging requires replacement of the circuit board"

Any ideas folks before I just put a cable between the two relays and manually switch it ?
Thanks in advance.