multi stage voltage regulator field voltage

[CAPAZ]

am trouble shooting an alternator on my engine that has quit.

it is a Leece-Neville around 160 amp. I had it rebuilt knowing it was about time and it did not excite when I replaced it.

I have a older BEP Marine (NZ) ER 4 multi-stage VR. When trouble shooting I noted no current coming from the field wire and no LED lights on the VR. Tracked that back to a blown fuse at the ignition panel (5 amp). After replacing the VR came on but when I tested the field voltage it was only putting out 3.5v.
not enough to excite the alternator.

SO my sense is the VR is not performing correctly but I am curious if anyone knows what that would mean, other than replacing the VR (or repair?)

I did jump power directly to the alternator at 12v and it went to full field, tach working etc.

any help would be much appreciated

cap'n rob (not ron)