many thanks for the replies
its 12.5 with the engine running . I have one of these cheap lidl/aldi battery testers it says 1/2 charged but none of the charging lights come on at all . Checked on my rover 75 car and it works fine on there.
I checked the voltage ith the engine switched off 12.5 on the big alternator terminal to the battery negative and to a good earth . No reading on the small terminal.
Engine running 12.4 v on both terminals but the lidl device still says no charge .
It was supposed to be a brand new alternator still in the box bought new last year and kept in my garage .
Is there any way i can check the alternator off the motor ?
years ago you used to feed positive power to a 2.2 w bulb then through the bulb to the alternator small terminal then connect the big one to the battery positive ,earth the alternator body to the same battery ,turn the alternator with a drill ant see if the voltage rise .
Seems odd the old one wasnt charging and now the new one not charging .
BTW auto eletrician shops thin on the ground around here .
As an aside she wont idle nicely at low revs 750 indicated sounds as though shes not running on all cylinders and rattles like big ends at the front of the engine knocking . Oil changed every 15000 miles and filters . with the serpentine belt off no rattles and no misfiring . The noise seems to come from the front of the engine .
its a 1999 manual diesel 146,000 miles .
I see on here someone said it could be the dual mass flywheel giving the crank wrong signals ? cant see why that is when the rattle ,hunting dissappears with the belt off.
Any,all help GRATEFULLY received
,,,,the big pulley at the bottom the belts go on there rubber and break up 
