Is it normal to see some air bubbles in the sight glass when the AC is ON, and the fans are running. When the Compressor is ON and the fans or OFF, there are no visible bubbles.

Also, when the Compressor is ON, the liquid refrigerant level as seen in the sight glass is about 1/4" below the glass. Is that normal, or should it be right at the top?

For all of the above the Ambient temperature was 23C (74F)

Thanks,

Phillip

__________________
'95 E300 Diesel, 264,000 Miles. [Sold it]

Yes, bubbles are normal for car with R-134a refrigerant (i.e. yours). You cannot correctly charge an R-134a car using the sight glass - as a result, sight glass has been eliminated on newer driers. What you are seeing is not air bubbles, but rather an emulsion of oil and refrigerant.

- JimY

Sight glass is useful for an R12 system - I don't even hook the gauges up, just top off until the "foamy" appearance is minimized (usually about a pound for my 300E).

For a R134A system, you really need to hook the gauges up and check the pressures for correct charge. My 380SE is a converted system and still has the sight glass. With perfect charge, it still looks "foamy" in the sight glass. If I kept adding refrigerant until the foam went away, the system would blow up!

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280