Check the site glass window on the top of the receive dryer bottle and with the AC running see if you see any bubbles.

It makes me wonder if you have a leak in your AC unit under the dash..... the AC has oil in the lines.

Haasman

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'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)