See No Bubbless
Brother of The Benz, fredsegal
Freon is colorless and odor free.
You may be seeing bubbles that have the appearance white.
The little glass window on your A/C drier reciever unit is to determine whiether your A/C is full of refrigarant or in need of filling.
When the glass shows nothing, the A/C is either full or low and should be serviced.
A simple test is to have the A/C at minimum cold setting, the fan on high(it goes to high speed with minimum temp setting), doors and windows up and closed.
Allow the unit to come to operating condition.
With someone in the front seat, have them to press the economy button while you watch the SIGHT GLASS and see what happens. If the unit is full, you won't see anything except the fluid dropping. Have the helper to press A/C button and watch again; fluid will rise meaning the unit is full or fall away showing bubbles or in your condition very low and should be service post hast to prevent damage to the compressor.
Hope this helps
Happy Trails Beep Beep from The Spiderman in Houston!!!