Can't help you on the sight glass David.
Doesn't your readout only tell you the cabin temp? You really need a thermometer to stick in the A/C vent to get a proper reading. Remember, once the chilled air leaves the ductwork, it is warmed by the cabin air, which in turn is warmed by solar energy via the window glass.
Now if we could only turn that solar energy into motor fuel, we wouldn't need gas, 300 days out of the year here in SoCal
'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.