Did you replace the brush pack (voltage regulator) when the alternator was rebuilt?

You should be showing about 13.5V at idle using a multimeter, anything lower points to the alternator or voltage regulator being on the outs. My money is on the regulator.

__________________
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.