defender 300tdi 100amp alternator , just fitted a VDO 0-4000 rpm gauge , every search says 1 + 3 off and 2 on or up/down . Mine the dips are all off giving me approx 780rpm tick-over and no load rev blip over 3000 rpm .
Now it seems fine , But why are my dips all 3 off , is this correct . Or if it wasn't correct would it be wildly off .

Are you taking the feed off the alternator?